Non-ionomeric silane crosslinked polyolefin golf ball layers

ABSTRACT

The present invention relates to golf balls, and in particular, to golf balls having at least one portion formed from at least one non-ionomeric, silane-crosslinked polyolefin materials that are formed in the presence of moisture or water during golf ball construction. The present invention also relates to methods of forming golf balls having at least one portion formed from at least one non-ionomeric, silane-crosslinked polyolefin materials that are formed in the presence of moisture or water.

FIELD OF THE INVENTION

The present invention relates to golf balls, and in particular, to golfballs having at least one portion formed from at least onenon-ionomeric, silane-crosslinked polyolefin materials that are moisturecured during golf ball construction.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into several general classes: (a)solid golf balls having one or more layers, and (b) wound golf balls.Solid golf balls include one-piece balls, which are easy to constructand relatively inexpensive, but have poor playing characteristics andare thus generally limited for use as range balls. Two-piece balls areconstructed with a generally solid core and a cover and are generallypopular with recreational golfers because they are very durable andprovide maximum distance. Balls having a two-piece construction arecommonly formed of a polymeric core encased by a cover. Solid golf ballsalso include multi-layer golf balls that are comprised of a solid coreof one or more layers and/or a cover of one or more layers. These ballsare regarded as having an extended range of playing characteristics.These balls are generally easy to manufacture, but are regarded ashaving limited playing characteristics.

A variety of golf balls designed to provide a wide range of playingcharacteristics, i.e., the compression, velocity, “feel,” and spin, thatcan be optimized for various playing ability, are known in the priorart. In the past, many expert golfers prefer golf balls having balatacovers because they provide a combination of distance, high spin rate,and control. However, balata is easily damaged in normal play and, thus,lacks the durability required by the average golfer. In contrast,amateur golfers generally prefer a solid, two-piece ball with an ionomercover because it provides a desirable combination of distance anddurability. Although ionomer covers are highly durable, they exhibit ahard “feel,” which many golfers find unacceptable, and a lower spinrate, making these balls more difficult to draw or fade. The differencesin the spin rate can be attributed to the differences in the compositionand construction to both the cover and the core.

Ionomeric and urethane covers currently dominate the golf ball market.However, there is a continuing need for a golf ball having desirableperformance characteristics, such as durability, spin rate and feel,while having a low cost and ease of manufacture. The golf balls of thepresent invention provide such desirable performance characteristics anddurability using novel compositions.

SUMMARY OF THE INVENTION

The present invention relates to a golf ball having a golf ballcomponent comprised of at least one non-ionomeric silane-crosslinkedpolyolefin, wherein the at least one non-ionomeric silane-crosslinkedpolyolefin is formed from contacting at least one silane-graftedpolyolefin with moisture or water. In particular, the golf ballcomponent is a core, an intermediate layer or a cover layer. Once thesilane-grafted polyolefin is crosslinked, the resultingsilane-crosslinked polyolefin is thermoset.

The silane-crosslinked polyolefin comprises a polyolefin selected fromthe group consisting of polymers, copolymers and terpolymers derivedfrom C₁-C₁₂ olefin monomer units, or a mixture thereof. Preferably, thepolyolefin is selected from the group consisting of low-densitypolyethylene, high-density polyethylene, linear low-densitypolyethylene, ultra high molecular weight polyethylene, metallocenepolyethylene, cross-linked polypropylene, ethylene-vinyl acetatecopolymer, ethylene-vinyl alcohol copolymer, ethylene ethylacrylatecopolymer, ethylene methylacrylate copolymer, ethylene acrylic acidcopolymers, ethylene methacrylic acid copolymer, ethylene-propylenecopolymer, ethylene propylene rubber, ethylene-propylene diene monomerrubber, chlorinated polyethylene, chlorosulfonated polyethylene,rubber-toughened olefin polymers, non-neutralized acid copolymers,styrenelbutadiene/styrene block copolymers,styrene/ethylene-butadiene/styrene block copolymers, ethylene vinylacetates, ethylene methyl acrylates, a metallocene-catalyzed polyolefinand mixtures thereof.

In one embodiment, the at least one silane-grafted polyolefin is formedfrom a polyolefin and at least one silane having at least onehydrolysable moiety and at least one vinyl group. In a preferredembodiment, the at least one silane has a formula of:

wherein R′ is a non-hydrolysable organofunctional group, X is ahydrolysable group, and n is 0-24. Preferably, R′ is a vinyl group and Xis selected from the group consisting of alkoxy, acyloxy, halogen,amino, hydrogen, ketoximate group, amido group, aminooxy, mercapto, andalkenyloxy. More preferably, X is an alkoxy represented by the formulaRO—, and wherein R is selected from the group consisting of a linear orbranched C₁-C₈ alkyl group, a C₆-C₁₂ aromatic group, and R³C(O)—,wherein R³ is a linear or branched C₁-C₈ alkyl group.

In one embodiment, the silane has the formula R′—(CH₂)_(n)SiX_(k)Q_(m)or [R′—(CH₂)_(n)]₂Si(X)_(p)Q_(q), wherein R′ is an unsaturated vinylgroup; Q is selected from the group consisting of an isocyanatefunctionality, i.e., monomeric, biuret, or isocyanurate, a glycidyl, ahalo group and —NR¹R², wherein R¹ and R² are each independently selectedfrom the group consisting of H, a linear or branched C₁-C₈ alkyl group,a linear or branched C₁-C₈ alkenyl group and a linear or branched C₁-C₈alkynyl group; X is a hydrolysable group; and n is 0-24, k is 1-3, m is3-n, p is 1-2 and q is 2-p. Preferably, X is alkoxy, acyloxy, halogen,amino, hydrogen, ketoximate group, amido group, aminooxy, mercapto, andalkenyloxy.

Preferably, the vinyl group is represented by the formula:

wherein R¹, R², and R³ are each independently selected from the groupconsisting of a substituted or unsubstituted linear or branched C₁-C₈alkyl group, a substituted or unsubstituted C₆-C₁₂ aromatic group and ahalo group, and wherein the substituted linear or branched C₁-C₈ alkylgroup and the substituted C₆-C₁₂ aromatic group is substituted with atleast one C₁-C₆ alkyl group, halo group, amine, CN, C₁-C₆ alkoxy group,or trihalomethane group.

Preferred silanes are selected from the group consisting ofvinyltrimethoxysilane, vinyldimethoxysilane, vinyltrimethoxysilane,vinylmethoxysilane, vinyltriethoxysilane, vinyldiphenylchlorosilane,vinyltrichlorosilane, vinylsilane, (vinyl)(methyl)diethoxysilane,vinyltriacetoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltriphenylsilane, and (vinyl)(dimethyl)chlorosilane. The at least onesilane is present from about 0.1 weight percent to about 100 weightpercent of the polyolefin.

In one embodiment, the silane-grafted polyolefin is formed from apolyolefin and at least one silane having at least one hydrolysablemoiety and at least one vinyl group in the presence of a free radicalsource selected from the group consisting of di-tert-amyl peroxide,di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and a mixture thereof. Typically,the free radical source is present from about 0.1 weight percent toabout 15 weight percent of the silane. In another embodiment, thesilane-crosslinked polyolefin is formed from contacting at least onesilane-grafted polyolefin with moisture or water in the presence of acrosslinking catalyst, wherein the crosslinking catalyst is a tincatalyst.

In one embodiment, the crosslinking catalyst is present in an amountfrom about 0.1 weight percent to about 15 weight percent of thesilane-grafted polyolefin. Preferably, the crosslinking catalyst is atin catalyst is selected from the group consisting of alkyltin oxides,tin carboxylates, alkyltin carboxylates and a mixture thereof.

In one embodiment, the core has a diameter of from about 1.200 inches toabout 1.630 inches and the cover has a thickness from about 0.02 inchesto about 0.35 inches. In another embodiment, the core has a hardness offrom about 50 Shore A to 90 Shore D, the intermediate layer has ahardness of from about 30 Shore D to about 90 Shore D, and the cover hasa hardness of from about 20 Shore A to about 70 Shore D. In yet anotherembodiment, the golf ball has a coefficient of restitution of about 0.7or more.

The present invention is also directed to a golf ball comprising a core;a cover disposed about the core; and optionally an intermediate layerdisposed between the core and the cover, wherein at least one of thecore, cover or optional intermediate layer comprises at least onesilane-crosslinked polyolefin. Preferably, the at least onesilane-crosslinked polyolefin is formed from contacting at least onesilane-grafted polyolefin with moisture or water. In one embodiment, thesilane-crosslinked polyolefin comprises a polyolefin selected from thegroup consisting of polymers, copolymers and terpolymers derived fromC₁-C₁₂ olefin monomer units, or a mixture thereof. Typically, thesilane-crosslinked polyolefin is thermoset.

The present invention also encompasses a method of forming a golf ballcomponent comprising the steps of: providing at least one silane-graftedpolyolefin; forming the golf ball component comprising the at least onesilane-grafted polyolefin; contacting the at least one silane-graftedpolyolefin, moisture or water, and a crosslinking catalyst to form asilane-crosslinked polyolefin. Preferably, the at least onesilane-grafted polyolefin is formed by contacting one or morepolyolefins or one or more polyolefins polymerized using a metallocenecatalyst; at least one silane having at least one hydrolysable moietyand at least one vinyl group; and free radical initiator; or contactingat least one C₁-C₁₂ monomer of a polyolefin, at least one silane havingat least one hydrolysable moiety and at least one vinyl group, andoptionally a metallocene catalyst or free radical source. Preferably,the at least one C₁-C₁₂ olefin monomer unit is selected from the groupconsisting of ethylene, propylene, butylene, isobutylene, pentene,isopentene, neopentene, hexene, heptene, octene, norbornene, monomers ofacid copolymers that do not become part of an ionomeric copolymer,ethylene vinyl acetate, ethylene methyl acrylate, and mixtures thereof.

In one embodiment of the method, the at least one silane has a formulaof:

wherein X is a hydrolysable group, and n is 0-24; wherein R′ is a vinylgroup represented by the formula:

wherein R¹, R², and R³ are each independently selected from the groupconsisting of a substituted or unsubstituted linear or branched C₁-C₈alkyl group, a substituted or unsubstituted C₆-C₁₂ aromatic group and ahalo group; and wherein the substituted linear or branched C₁-C₈ alkylgroup and the substituted C₆-C₁₂ aromatic group is substituted with atleast one C₁-C₆ alkyl group, halo group, amine, CN, C₁-C₆ alkoxy group,or trihalomethane group. In a preferred embodiment of the method, X isselected from the group consisting of alkoxy, acyloxy, halogen, amino,hydrogen, ketoximate group, amido group, aminooxy, mercapto, andalkenyloxy.

In another preferred embodiment of the method, the free radicalinitiator is selected from the group consisting of di-tert-amylperoxide, di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and a mixture thereof, wherein thefree radical source is present from about 0.1 weight percent to about 15weight percent of the silane; and wherein the polyolefin is selectedfrom the group consisting of low-density polyethylene, high-densitypolyethylene, linear low-density polyethylene, ultra high molecularweight polyethylene, metallocene polyethylene, cross-linkedpolypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcoholcopolymer, ethylene ethylacrylate copolymer, ethylene methylacrylatecopolymer, ethylene acrylic acid copolymers, ethylene methacrylic acidcopolymer, ethylene-propylene copolymer, ethylene propylene rubber,ethylene-propylene diene monomer rubber, chlorinated polyethylene,chlorosulfonated polyethylene, rubber-toughened olefin polymers,non-neutralized acid copolymers, styrene/butadiene/styrene blockcopolymers; styrene/ethylene-butadiene/styrene block copolymers,ethylene vinyl acetates, ethylene methyl acrylates, ametallocene-catalyzed polyolefin and mixtures thereof.

In a preferred embodiment of the method, the golf ball component is acore layer, an intermediate layer, or a cover layer and is formed byinjection molding or compression molding the at least one silane-graftedpolyolefin. In another preferred embodiment of the method, thecrosslinking catalyst is a tin catalyst, wherein the tin catalystselected from the group consisting of an alkyltin oxide, a tincarboxylate, an alkyltin carboxylate, and mixtures thereof and whereinthe crosslinking catalyst is present in amounts from about 0.1 weightpercent to about 15 weight percent of the silane-grafted polyolefin.

In a preferred embodiment of the method, the at least one silane-graftedpolyolefin is contacted with moisture at from about 30% to 100% relativehumidity and at a temperature between about 20° C. to about 100° C. fora time sufficient to substantially complete the crosslinking between thesilane-grafted polyolefins. Preferably, the relative humidity is betweenabout 50% to about 80% and the time is between about 30 minutes to about24 hours. In another embodiment, the golf ball component is formed byinjection molding or compression molding.

The present invention also encompasses a method of forming a golf ballcomponent comprising the steps of: contacting at least one silane, atleast one polyolefin, at least one free radical initiator, at least onecrosslinking catalyst, and water or moisture to form a reaction mixture;and forming the golf ball component comprising the reaction mixture.Preferably, the reaction mixture forms at least one silane-graftedpolyolefin that is crosslinked.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to one-piece golf balls, two-piece golfballs, or multilayer golf balls having a center, at least oneintermediate layer disposed concentrically adjacent to the center, and acover. The invention also relates to golf balls having a double core, amulti-layer core, a double cover, a multi-layer cover or more than oneintermediate layer. At least one portion of the golf ball, i.e., one ofthe center, cover(s), or intermediate layer(s), comprises at least onenon-ionomeric, silane-crosslinked polyolefin.

The present invention relates to the use of at least one non-ionomeric,silane-crosslinked polyolefin in golf ball layers or components,including covers, cores, and intermediate layers. As used herein, theterm “polyolefin” refers to polyolefin homopolymers, polyolefincopolymers, polymers containing three or more different olefins, andmixtures thereof. The present invention further relates to a golf ballhaving at least one layer in at least one of cover layer, core or corelayer, or one or more optional intermediate layers, where the layer isformed from a composition comprising at least one non-ionomeric,silane-crosslinked polyolefin.

Compositions of the Invention

In particular, the compositions of the present invention can be formedby grafting one or more silanes to one or more polyolefins to form asilane-grafted polyolefin, and the silane-grafted polyolefin is furthercrosslinked in the presence of water or moisture. Alternatively, thecompositions of the present invention can be formed by copolymerizingone or more silanes with one or more monomers of the polyolefins to forma silane-grafted polyolefin, preferably in the presence of a catalystsuch as a peroxide, and the silane-grafted polyolefin is furthercrosslinked in the presence of water or moisture. The present inventionis advantageous over other typical methods of crosslinking polyolefins,such as by peroxide or irradiation, because it avoids the problemsassociated with these other typical methods. In particular, water ormoisture cure/crosslinking avoids: limitations in the types of additivesthat can be utilized (antioxidants cannot be added toperoxide-crosslinked polyolefins); the high cost of installing andoperating equipment; low outputs; the use of radiation; and hazardousoperating conditions and advantageously provides: easy control ofcrosslinking density; and greater uniformity of cure or crosslinkingthroughput. Typically, the silane-crosslinked polyolefins are formed byapplying reactants to a golf ball or golf ball precursor and thenreacting the reactants to form the silane-crosslinked polyolefin layer.

Many thermoplastic polymers, such as various polyolefins, possessdesirable properties, such as excellent elasticity and thermalstability, toughness, low temperature ductility, UV resistance andrecyclability, but they are not suitable for high temperatureapplications due to loss of certain critical physical properties. Forexample, polyolefins such as polyethylene will soften and flow, and losesuch critical physical properties at elevated temperatures and therebylimiting its use. Without wishing to be bound to any theory,crosslinking changes such polyolefin polymers from thermoplastic tothermoset to give a non-melting, more durable polymer having desirableproperties, such as increasing environmental stress cracking resistance,and heat resistance, environmental stress crack resistance, creepresistance and abrasion resistance.

The non-ionomeric, silane-crosslinked polyolefins of the presentinvention are partially or completely crosslinked by water or moisturecure of silane moieties that are grafted onto polyolefins. One or morepolyolefins can be the base material of the non-ionomeric,silane-crosslinked polyolefins and can be any polyolefin known to theskilled artisan. In particular, the polyolefin includes, but is notlimited to, polymers, copolymers and terpolymers derived from C₁-C₁₂olefin monomer units in all their isomeric forms, or mixtures thereof,and includes, for example, monomers selected from the group consistingof ethylene, propylene, butylene, isobutylene, pentene, isopentene,neopentene, hexene, heptene, octene, norbornene, and the like, as wellas rubber-toughened olefin polymers, acid copolymers that do not becomepart of an ionomeric copolymer, and thermoplastic elastomers such as SBS(styrene/butadiene/styrene) or SEBS (styrene/ethylene-butadiene/styrene)block copolymers, including KRATON® (Shell), dynamically vulcanizedelastomers such as SANTOPRENE® (Monsanto), ethylene vinyl acetates suchas ELVAX® (DuPont), and ethylene methyl acrylates such as OPTEMA®(Exxon), and the like, and mixtures thereof. Accordingly, thepolyolefins include, but are not limited to, polyethylene,polypropylene, polybutylene, polypentene, polyhexene, polyheptene,polyoctene, or polynorbornene. In one embodiment, the non-ionomericpolyolefins can be mixed with ionomers known to one of ordinary skill inthe art.

In a preferred embodiment, the polyolefin is polyethylene. Preferably,the polyethylene is selected from the group consisting of a low-densitypolyethylene, high-density polyethylene (HDPE), linear low-densitypolyethylene (LLDPE), ultra high molecular weight polyethylene,metallocene polyethylene, cross-linked polypropylene, ethylene-vinylacetate copolymer (EVA), ethylene-vinyl alcohol copolymer, ethyleneethylacrylate copolymer, ethylene methylacrylate copolymer, ethyleneacrylic acid copolymers, ethylene methacrylic acid copolymer,ethylene-propylene copolymer, ethylene propylene rubber (EPR),ethylene-propylene diene monomer rubber (EPDM), chlorinatedpolyethylene, chlorosulfonated polyethylene, and mixtures thereof.

In another embodiment, the polyolefins are made by a metallocenecatalyst, such as EXACT® material available from EXXON. As used herein,the term “metallocene catalyzed polymer” refers to any polymer,copolymer or terpolymer, and, in particular, any polyolefin, polymerizedusing a metallocene catalyst. Such metallocene-catalyzed polyolefinsinclude polyethylene, polypropylene, polybutylene and copolymers such asethylene methylacrylate, ethylene ethylacrylate, ethylene vinyl acetate,ethylene methacrylic or ethylene acrylic acid or propylene acrylic acidand copolymers and homopolymers produced by contacting the appropriatemonomer or monomers with a single-site catalyst or a metallocenecatalyst.

The silanes of the present invention have at least one hydrolysablemoiety, such as an alkoxy or carboxy group, and at least one vinylgroup. The vinyl group enables the silane to be grafted onto thepolyolefin and the hydrolysable moiety provide the crosslinking site. Inone embodiment, the silanes further include at least one amino group,isocyanate functional group, glycidyl group, or a mixture thereof. Suchadditional groups allow for adhesional and performance modifications.

Preferred silanes include, but are not limited to, compounds having theformula:

wherein R′ is a non-hydrolysable organofunctional group, X is ahydrolysable group, and n is 0-24. The non-hydrolysable organofunctionalgroup typically can link (either by forming a covalent or by anotherbinding mechanism, such as hydrogen bond) to a polymer, such as apolyolefin, thereby attaching the silane to the polymer. R′ ispreferably a vinyl group. X is preferably alkoxy, acyloxy, halogen,amino, hydrogen, ketoximate group, amido group, aminooxy, mercapto,alkenyloxy group, and the like. Preferably, X is an alkoxy, RO—, whereinR is selected from the group consisting of a linear or branched C₁-C₈alkyl group, a C₆-C₁₂ aromatic group, and R³C(O)—, wherein R³ is alinear or branched C₁-C₈ alkyl group. Typically, the silane can belinked to the polymer in one of two ways: by reaction of the silane tothe finished polymer or copolymerizing the silane with the polymerprecursors.

In another embodiment, the silane has the formulaR′—(CH₂)_(n)SiX_(k)Q_(m) or [R′—(CH₂)_(n)]₂Si(X)_(p)Q_(q), wherein R′ isan unsaturated vinyl group; Q is selected from the group consisting ofan isocyanate functionality, i.e., a monomer, a biuret, or anisocyanurate; a glycidyl, a halo group and —NR¹R², wherein R¹ and R² areeach independently selected from the group consisting of H, a linear orbranched C₁-C₈ alkyl group, a linear or branched C₁-C₈ alkenyl group anda linear or branched C₁-C₈ alkynyl group; X is a hydrolysable group; andn is 0-24, k is 1-3, m is 3-n, p is 1-2 and q is 2-p. X is preferablyalkoxy, acyloxy, halogen, amino, hydrogen, ketoximate group, amidogroup, aminooxy, mercapto, alkenyloxy group, and the like. Preferably,the halo group is fluoro, chloro, bromo or iodo and is preferablychloro.

In a preferred embodiment, the unsaturated vinyl group A is representedby the formula:

wherein R¹, R², and R³ are each independently selected from the groupconsisting of a substituted or unsubstituted linear or branched C₁-C₈alkyl group, a substituted or unsubstituted C₆-C₁₂ aromatic group and ahalo group. Preferred halo groups include F, Cl or Br. The C₁-C₈ alkylgroups and the C₆-C₁₂ aromatic groups may be substituted with one ormore C₁-C₆ alkyl groups, halo groups, such as F, Cl and Br, amines, CN,C₁-C₆ alkoxy groups, trihalomethane, such as CF₃ or CCl₃, or mixturesthereof. Preferably, R¹, R², and R³ are each independently selected fromthe group consisting of hydrogen, methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl and tert-butyl. More preferably, R¹, R², and R³ areeach independently hydrogen or methyl.

Thus in a preferred embodiment, the silane is a vinyltrialkoxysilane,such as vinyltrimethoxysilane, vinyldimethoxysilane,vinyltrimethoxysilane, vinylmethoxysilane, vinyltriethoxysilane,vinyldiphenylchlorosilane, vinyltrichlorosilane, vinylsilane,(vinyl)(methyl)diethoxysilane, vinyltriacetoxysilane,vinyltris(2-methoxyethoxy)silane, vinyl triphenylsilane, and(vinyl)(dimethyl)chlorosilane.

The silanes of the present invention are present from about 0.1 weightpercent to about 100 weight percent of the polyolefin. Typically, thesilanes are present from about 0.5 weight percent to about 50 weightpercent of the polyolefin, preferably from about 1 weight percent toabout 20 weight percent of the polyolefin, more preferably from about 2weight percent to about 10 weight percent of polyolefin and even morepreferably from about 3 weight percent to about 5 weight percent. Asused herein, all upper and lower limits of the ranges disclosed hereincan be interchanged to form new ranges. Thus, the present invention alsoencompasses silane amounts of from about 0.1 weight percent to about 5weight percent of polyolefin, from about 1 weight percent to about 10weight percent of polyolefin, and even from 20 weight percent to about50 weight percent.

Commercially available silanes for moisture crosslinking may be used toform golf ball components and golf balls. A nonlimiting example of asuitable silane is SILCAT® RHS Silane, a multi-component crosslinkingsystem for use in moisture crosslinking of stabilized polyethylene orethylene copolymers (available at Crompton Corporation, Middlebury,Conn.). IN addition, functionalized resin systems also may be used, suchas SYNCURE®, which is a silane-grafted, moisture-crosslinkablepolyethylene system available from PolyOne Corporation of Cleveland,Ohio, POLIDAN®, which is a silane-crosslinkable HDPE available fromSolvay of Padanaplast, Italy, and VISICO™/AMBICA™, which is apolyethylene system that utilizes a non-tin catalyst in crosslinkingavailable from Borealis of Denmark.

The present invention also is directed to a method of forming a golfball having at least one golf ball component comprised of one or moresilane-crosslinked polyolefins. In particular, the present invention isdirected to a method of forming core layers, intermediate layers, orcover layers that are comprised of one or more silane-crosslinkedpolyolefins, wherein the silane-crosslinked polyolefins are comprised ofone or more silane-grafted polyolefins. Especially preferred golf ballcomponents are cover layers and intermediate layers.

Thus according to the present invention, the silane-grafted polyolefinscan be formed by grafting one or more silanes onto one or morepolyolefins and/or one or more polyolefins polymerized using ametallocene catalyst, and subsequently crosslinking the silane-graftedpolyolefins by contacting the silane-grafted polyolefins with moistureor water to form the silane-crosslinked polyolefin. In the graftingstep, at least one silane of the present invention is contacted with atleast one polyolefin and/or metallocene-catalyzed polyolefin in thepresence of a free radical source that acts as a grafting initiator.Typically, the reaction is carried out at a temperature that is greaterthan the decomposition temperature for the utilized peroxide, which isreadily ascertainable by one of ordinary skill in the art.

Without wishing to be bound to any theory, the grafting step attachesthe silane to the polyolefin via the vinyl group to form asilane-grafted polyolefin, as shown in the example equation below. R¹,R², R³, X, n and m are described hereinabove.

The silane-grafted polyolefins can be injection molded as a layer usingmethods known to one of ordinary skill in the art, or formed into a cup(to be compression molded prior to final crosslinking) prior to beingcontacted with water or moisture for hydrolytic crosslinking.

In another embodiment, the silane-grafted polyolefins can be formed bypolymerizing one or more silanes with one or more monomers ofpolyolefins, optionally in the presence of one or more metallocenecatalysts and/or a free radical source, to form a silane-graftedpolyolefin.

In an alternative embodiment, the silane-grafted polyolefins can beformed by grafting one or more silanes onto monomers of the polyolefinsto form silane-grafted monomers, preferably in the presence of at leastone free radical source as the grafting initiator; polymerizing thesilane-grafted monomers, optionally in the presence of one or moremetallocene catalysts, to form a silane-grafted polyolefin. In yetanother embodiment, the silane-grafted monomers can be copolymerizedwith ungrafted monomers of polyolefins, i.e., polyolefin monomers thatare not grafted with silane, to form a copolymer that containssilane-grafted copolymer units linked with ungrafted copolymer units.

Accordingly, silanes can be grafted by contacting one or more silanes ofthe present invention with C₁-C₁₂ olefin monomer units, in all theirisomeric forms, in the presence of at least one free radical source as agrafting initiator. Preferred C₁-C₁₂ olefin monomer units include, forexample, monomers selected from the group consisting of ethylene,propylene, butylene, isobutylene, pentene, isopentene, neopentene,hexene, heptene, octene, norbornene, and the like, as well as monomersof acid copolymers that do not become part of an ionomeric copolymer,and thermoplastic elastomers, such as SBS or SEBS block copolymers,ethylene vinyl acetates, ethylene methyl acrylates, and the like, andmixtures thereof.

Suitable free radical sources include organic peroxides, whichfacilitates grafting of the silane onto the polyolefin backbone.Examples of suitable peroxides are provided below:

In particular, suitable free-radical sources include organic peroxidecompounds, such as di-tert-amyl peroxide,di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy) diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butylperoxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and the like, and any mixturethereof. In one embodiment, the free radical sources is ahydrogen-abstracting peroxides.

The free radical source may be present in an amount greater than about0.1 parts per hundred of the total silane component, preferably about0.1 to about 15 parts per hundred of the total silane component, andmore preferably about 0.2 to about 5 parts per hundred of the totalsilane component, and most preferably between about 0.3 to about 2 partsper hundred of the total silane component.

In one embodiment, the amount of free radical source is about 5 partsper hundred or less, but also may be about 3 parts per hundred or less.In another embodiment, the amount of free radical source is about 2.5parts per hundred or less. In yet another embodiment, the amount of freeradical source is about 2 parts per hundred or less. In still anotherembodiment, the amount of free radical source is about 1 parts perhundred or less preferably about 0.75 parts per hundred or less.

The silane-grafted polyolefins are contacted with moisture or water toform the silane-crosslinked polyolefin. In particular, thesilane-grafted polyolefins contain one or more hydrolysable groups,which upon contact with moisture or water and optionally in the presenceof a crosslinking catalyst, condenses and crosslinks other hydrolysablegroups on adjacent grafted polyolefins. Without wishing to be bound toany theory, the hydrolysable groups of the silane-grafted polyolefinsreact with water to form a silane crosslink or siloxane that chemicallylinks two or more adjacent silane-grafted polyolefins, as shown in theexample equation below:

The addition of water to the silane grafted polyolefins hydrolyze the Xgroups to form a silanol intermediate, which can further condense tochemically link adjacent silanes.

In another embodiment, the hydrolysable groups of a silane-graftedpolyolefin condense and crosslink with other hydrolysable groups on thesame silane-grafted polyolefin molecule.

Any crosslinking catalyst that facilitates the condensation of thehydrolysable groups of the silane-grafted polyolefins known to one ofordinary skill in the art can be used. Particular crosslinking catalystsinclude, but are not limited to, tin catalysts, platinum catalysts, acidcatalysts, and other non-tin catalysts, such as AMBICAT™ (available atBorealis, Denmark). Tin catalysts include alkyltin oxides, tincarboxylates, or alkyltin carboxylates. Preferred alkyltin oxides andalkyltin carboxylates are comprised of linear or branched C₁-C₈ alkylgroups. Preferred tin carboxylates and alkyltin carboxylates arecomprised of C₁-C₂₄ carboxylate groups. Particularly preferred tincatalysts include tributyltin oxide, tributyltin laurate, dibutyltindilaurate, and mixtures thereof.

Crosslinking catalysts are typically present in amounts from about 0.1weight percent to about 15 weight percent of the silane-graftedpolyolefin, preferably from about 0.3 weight percent to about 10 weightpercent of the silane-grafted polyolefin, more preferably from about 0.5weight percent to about 5 weight percent of the silane-graftedpolyolefin, and even more preferably from about 1 weight percent toabout 3 weight percent of the silane-grafted polyolefin.

The silane-grafted polyolefins typically are exposed to from about 30%to saturated (i.e., 100%) relative humidity, at a temperature betweenabout 20° C. to about 100C for a time sufficient to substantiallycomplete the crosslinking between the silane-grafted polyolefins.

In one embodiment, the relative humidity is between about 40% to about90% relative humidity. In another embodiment, the relative humidity isbetween about 50% to about 80%. In yet another embodiment, the relativehumidity is between about 60% to about 70%.

In one embodiment, the temperature at which the silane-graftedpolyolefins are contacted with moisture or humidity is between about 30°C. to about 90° C. In other embodiments, the temperature at which thesilane-grafted polyolefins are contacted with moisture or humidity isbetween about 40° C. to about 80° C., from about 50° C. to about 75° C.and even from about 60° C. to about 70° C. In another embodiment, thesilane-grafted polyolefins are contacted with moisture or water in anautoclave at temperatures exceeding 100° C., including temperatures ofup to 300° C. to 500° C.

Increasing the relative humidity and/or temperature accelerates the timerequired to substantially complete the crosslinking. For example, thesilane-grafted polyolefins are contacted with moisture at 80% relativehumidity at 70° C. for between about 30 minutes to about 3 hours tosubstantially complete crosslinking, while contact with moisture at 100%relative humidity at 70° C. would require between about 15 minutes andabout 1 hour to substantially complete crosslinking. The crosslinkingtimes and temperatures depend on the thickness and composition and isreadily modified by one of ordinary skill in the art.

In one embodiment, the silane crosslinked polyolefin golf ball layer isprepared in a one-step process, also known as the Monosil Process, asdescribed in “Syncure™: Silane-Grafted Moisture-CrosslinkablePolyethylene,” Technical Service Report Number 66, PolyOne Corporation,October 2002. In particular, the silane grafting and crosslinking occursduring the fabrication of the golf ball layer. Thus, the silane, freeradical initiator, polyolefin, catalyst, and optional antioxidants, aremixed to form a reaction mixture that directly is used to form the golfball layer while contacting the reaction with water or moisture. Forexample, the reaction mixture can be directly used to injection orcompression mold the golf ball layer.

In another embodiment, the silane crosslinked polyolefin golf ball layeris prepared in a two-step process, also known as the Sioplas Process, asdescribed in “Syncure™: Silane-Grafted Moisture-CrosslinkablePolyethylene,” Technical Service Report Number 66, PolyOne Corporation,October 2002. In particular, the first step involves grafting the silaneonto the polyolefin and comprises contacting the silane with thepolyolefin in the presence of a free radical initiator. The second stepinvolves crosslinking the silane-grafted polyolefin, which comprisescontacting the silane-grafted polyolefin with a crosslinking catalystand water or moisture and processing the crosslinked silane-graftedpolyolefin into a golf ball layer.

Golf Ball Construction

Core Layer(s)

As used herein, the term “core” means the innermost portion of a golfball, and may include one or more layers. When a multi-layer core iscontemplated, the core is the innermost component with one or moreadditional core layers disposed thereon. At least a portion of the core,typically the center, is solid, semi-solid, hollow, powder-filled orfluid-filled. As used herein, the term “fluid” means a gas, liquid, gel,paste, or the like, or a combination thereof.

The core or at least one core layer may be composed of one or moresilane-crosslinked polyolefins of the present invention and formed usingthe methods described herein. When the core or at least one core layeris not comprised of the silane-crosslinked polyolefins, it is composedconventional materials known to one of ordinary skill in the art may beused, including thermoplastic and thermosetting materials as discussedbelow. The one or more silane-crosslinked polyolefins also may beblended with conventional core materials.

Golf balls having a one-piece core or any portion of a multi-layer coremay be formed from any core material suitable for use in golf balls thatis known to one of ordinary skill in the art, as discussed below.Suitable core materials include thermoset materials, such as rubber,styrene butadiene, polybutadiene, including cis-polybutadiene,trans-polybutadiene, and blends thereof, as well as cis-to-transconverted polybutadiene, isoprene, polyisoprene, trans-isoprene, as wellas thermoplastics, such as ionomer resins, polyamides or polyesters, andthermoplastic and thermoset polyurethane elastomers, and any mixturethereof. In addition, suitable core materials include polyureacompositions, as well as other conventional materials, such ascompositions including a base rubber, a crosslinking agent, and adensity adjusting filler. The base rubber may include natural orsynthetic rubbers, as well as any combination thereof. In oneembodiment, the base rubber is 1,4-polybutadiene having a cis-structureof at least about 40 percent, of which natural rubber, polyisoprenerubber and/or styrene-butadiene rubber may be added thereto. The coremay also include one or more cis-to-trans catalyst and a free radicalsource, as well as a cis-to-trans catalyst accelerator and crosslinkingagent, as described in copending U.S. application Ser. Nos. 10/437,386and 10/437,387, the entirety of which are incorporated herein byreference.

The core may also include a filler. Fillers added to one or moreportions of the golf ball typically include processing aids or compoundsto affect rheological and mixing properties, the specific gravity (i.e.,density-modifying fillers), the modulus, the tear strength,reinforcement, and the like. The fillers are generally inorganic, andsuitable fillers include numerous metals (including metal powders) ormetal oxides, such as zinc oxide and tin oxide, as well as bariumsulfate, zinc sulfate, calcium carbonate, barium carbonate, clay,tungsten, tungsten carbide, an array of silicas, and mixtures thereof.Fillers may also include various foaming agents or blowing agents whichmay be readily selected by one of ordinary skill in the art. Foamedpolymer blends may be formed by blending ceramic or glass microsphereswith polymer material. Polymeric, ceramic, metal, and glass microspheresmay be solid or hollow, and filled or unfilled. Fillers are typicallyalso added to one or more portions of the golf ball to modify thedensity thereof to conform to uniform golf ball standards. Fillers mayalso be used to modify the weight of the center or at least oneadditional layer for specialty balls, e.g., a lower weight ball ispreferred for a player having a low swing speed.

Additional materials conventionally included in golf ball compositionsinclude, but are not limited to, density-adjusting fillers, coloringagents, reaction enhancers, whitening agents, UV absorbers, hinderedamine light stabilizers, defoaming agents, processing aids, and otherconventional additives. Stabilizers, softening agents, plasticizers,including internal and external plasticizers, impact modifiers, foamingagents, excipients, reinforcing materials and compatibilizers can alsobe added to any composition of the invention. All of these materials,which are well known in the art, are added for their usual purpose intypical amounts.

For example, the fillers discussed above may be added to theconventional materials to affect Theological and mixing properties, thespecific gravity (i.e., density-modifying fillers), the modulus, thetear strength, reinforcement, and the like. Fillers may also be used tomodify the weight of the core, e.g., a lower weight ball is preferredfor a player having a low swing speed.

The golf ball components may be formed using a variety of applicationtechniques such as compression molding, flip molding, injection molding,retractable pin injection molding, reaction injection molding (RIM),liquid injection molding (LIM), casting, vacuum forming, powder coating,flow coating, spin coating, dipping, spraying, and the like. A method offlip molding can be found, for example, in U.S. Pat. No. 6,096,255. Amethod of injection molding using a split vent pin can be found inco-pending U.S. patent application Ser. No. 09/742,435, filed Dec. 22,2000, entitled “Split Vent Pin for Injection Molding.” Examples ofretractable pin injection molding may be found in U.S. Pat. Nos.6,129,881, 6,235,230, and 6,379,138. A method of molding components formulti-layer core golf balls may be found in, for example, U.S. Pat. No.6,290,797. Each of these molding references are incorporated in theirentirety by reference herein. In addition, a chilled chamber, i.e., acooling jacket, such as the one disclosed in U.S. patent applicationSer. No. 09/717,136, filed Nov. 22, 2000, entitled “Method of MakingGolf Balls” may be used to cool the compositions of the invention whencasting, which also allows for a higher loading of catalyst into thesystem.

Conventionally, compression molding and injection molding are applied tothermoplastic materials, whereas RIM, liquid injection molding, andcasting are employed on thermoset materials. These and other manufacturemethods are disclosed in U.S. Pat. Nos. 6,207,784, 5,334,673, 5,484,870,and 5,733,428, the disclosures of which are incorporated herein byreference in their entirety.

The cores of the invention may be formed by any suitable method known toone of ordinary skill in art. When the cores are formed from a thermosetmaterial, compression molded is a particularly suitable method offorming the core. In a thermoplastic core embodiment, on the other hand,the cores may be injection molded.

Suitable methods include single pass mixing (ingredients are addedsequentially), multi-pass mixing, and the like. The crosslinking agent,and any other optional additives used to modify the characteristics ofthe golf ball center or additional layer(s), may similarly be combinedby any type of mixing. Suitable mixing equipment is well known to one ofordinary skill in the art, and such equipment may include a Banburymixer, a two-roll mill, or a twin screw extruder. Suitable mixing speedsand temperatures are well-known to one of ordinary skill in the art, ormay be readily determined without undue experimentation.

The mixture can be subjected to, e.g., a compression or injectionmolding process, and the molding cycle may have a single step of moldingthe mixture at a single temperature for a fixed-time duration. In oneembodiment, a single-step cure cycle is employed. Although the curingtime depends on the various materials selected, a suitable curing timeis about 5 minutes to about 18 minutes, preferably from about 8 minutesto about 15 minutes, and more preferably from about 10 minutes to about12 minutes. An example of a single step molding cycle, for a mixturethat contains dicumyl peroxide, would hold the polymer mixture at 171°C. (340° F.) for a duration of 15 minutes. An example of a two-stepmolding cycle would be holding the mold at 143° C. (290° F.) for 40minutes, then ramping the mold to 171° C. (340° F.) where it is held fora duration of 20 minutes. One of ordinary skill in the art will bereadily able to adjust the curing time based on the particular materialsused and the discussion herein.

Furthermore, U.S. Pat. Nos. 6,180,040 and 6,180,722 disclose methods ofpreparing dual core golf balls. The entire disclosures of these patentsare hereby incorporated by reference herein.

Intermediate Layer(s)

An “intermediate layer” (also known as inner layer or mantle layer) isdefined herein as a portion of the golf ball that occupies a volumebetween the cover and the core. Such an intermediate layer may bedistinguished from a cover or a core by some difference between the golfball layers, e.g., hardness, compression, thickness, and the like. Anintermediate layer may be used, if desired, with a multilayer cover or amultilayer core, or with both a multilayer cover and a multilayer core.Accordingly, an intermediate layer is also sometimes referred to in theart as an inner cover layer, as an outer core layer or as a mantlelayer, i.e., any layer(s) disposed between the inner core and the outercover of a golf ball, this layer may be incorporated, for example, witha single layer or a multilayer cover, with a one-piece core or amultilayer core, with both a single layer cover and core, or with both amultilayer cover and a multilayer core. As with the core, theintermediate layer may also include a plurality of layers. It will beappreciated that any number or type of intermediate layers may be used,as desired.

The intermediate layer may be comprised of silane-crosslinkedpolyolefins of the present invention and formed using the methodsdescribed herein. When an intermediate layer is not comprised of thesilane-crosslinked polyolefins of the present invention, it is composedconventional materials known to one of ordinary skill in the art may beused, including thermoplastic and thermosetting materials as discussedbelow. The one or more silane-crosslinked polyolefins also may beblended with conventional intermediate layer materials.

The intermediate layer typically is composed conventional materialsknown to one of ordinary skill in the art may be used, includingthermoplastic and thermosetting materials as discussed below.

The conventional intermediate layer can include any materials known toone of ordinary skill in the art including thermoplastic andthermosetting materials. For example, the intermediate layer may alsolikewise include one or more homopolymeric or copolymeric materials,such as:

-   -   (1) Vinyl resins, such as those formed by the polymerization of        vinyl chloride, or by the copolymerization of vinyl chloride        with vinyl acetate, acrylic esters or vinylidene chloride;    -   (2) Polyolefins, such as polyethylene, polypropylene,        polybutylene and copolymers such as ethylene methylacrylate,        ethylene ethylacrylate, ethylene vinyl acetate, ethylene        methacrylic or ethylene acrylic acid or propylene acrylic acid        and copolymers and homopolymers produced using a single-site        catalyst or a metallocene catalyst;    -   (3) Polyurethanes, such as those prepared from polyols and        diisocyanates or polyisocyanates and those disclosed in U.S.        Pat. No. 5,334,673;    -   (4) Polyureas, such as those disclosed in U.S. Pat. No.        5,484,870;    -   (5) Polyamides, such as poly(hexamethylene adipamide) and others        prepared from diamines and dibasic acids, as well as those from        amino acids such as poly(caprolactam), and blends of polyamides        with SURLYN, polyethylene, ethylene copolymers,        ethyl-propylene-non-conjugated diene terpolymer, and the like;    -   (6) Acrylic resins and blends of these resins with poly vinyl        chloride, elastomers, and the like;    -   (7) Thermoplastics, such as urethanes; olefinic thermoplastic        rubbers, such as blends of polyolefins with        ethylene-propylene-non-conjugated diene terpolymer; block        copolymers of styrene and butadiene, isoprene or        ethylene-butylene rubber; or copoly(ether-amide), such as PEBAX,        sold by Atofina Chemicals, Inc. of King of Prussia, Pa.;    -   (8) Polyphenylene oxide resins or blends of polyphenylene oxide        with high impact polystyrene as sold under the trademark NORYL        by General Electric Company of Pittsfield, Mass.;    -   (9) Thermoplastic polyesters, such as polyethylene        terephthalate, polybutylene terephthalate, polyethylene        terephthalate/glycol modified and elastomers sold under the        trademarks HYTREL by E.I. DuPont de Nemours & Co. of Wilmington,        Del., and LOMOD by General Electric Company of Pittsfield,        Mass.;    -   (10) Blends and alloys, including polycarbonate with        acrylonitrile butadiene styrene, polybutylene terephthalate,        polyethylene terephthalate, styrene maleic anhydride,        polyethylene, elastomers, and the like, and polyvinyl chloride        with acrylonitrile butadiene styrene or ethylene vinyl acetate        or other elastomers; and    -   (11) Blends of thermoplastic rubbers with polyethylene,        propylene, polyacetal, nylon, polyesters, cellulose esters, and        the like.

The intermediate layer also may include ionomeric materials, such asionic copolymers of ethylene and an unsaturated monocarboxylic acid,which are available under the trademark SURLYN® of E.I. DuPont deNemours & Co., of Wilmington, Del., or IOTEK® or ESCOR® of Exxon. Theseare copolymers or terpolymers of ethylene and methacrylic acid oracrylic acid totally or partially neutralized, i.e., from about 1 toabout 100 percent, with salts of zinc, sodium, lithium, magnesium,potassium, calcium, manganese, nickel or the like. The carboxylic acidgroups may also include methacrylic, crotonic, maleic, fumaric oritaconic acid. The salts are the reaction product of an olefin havingfrom 2 to 10 carbon atoms and an unsaturated monocarboxylic acid having3 to 8 carbon atoms.

The intermediate layer may also include at least one ionomer, such asacid-containing ethylene copolymer ionomers, including E/X/Y terpolymerswhere E is ethylene, X is an acrylate or methacrylate-based softeningcomonomer present in about 0 to 50 weight percent and Y is acrylic ormethacrylic acid present in about 5 to 35 weight percent.

The ionomer also may include so-called “low acid” and “high acid”ionomers, as well as blends thereof. In general, ionic copolymersincluding up to about 15 percent acid are considered “low acid”ionomers, while those including greater than about 15 percent acid areconsidered “high acid” ionomers.

Thermoplastic polymer components, such as copolyetheresters (e.g.,HYTREL®, available from DuPont), copolyesteresters, copolyetheramides(e.g., PEBAX®, available from Atofina Chemicals, Inc.) elastomericpolyolefins, styrene diene block copolymers and their hydrogenatedderivatives (e.g. block copolymers of styrene-butadiene-styrene,styrene-(ethylene-propylene)-styrene orstyrene-(ethylene-butadiene)-styrene, as well as KRATON D®, KRATON G®,KRATON FG® from Shell Chemical), copolyesteramides, thermoplasticpolyurethanes, such as copolyetherurethanes, copolyesterurethanes,copolyureaurethanes, epoxy-based polyurethanes, polycaprolactone-basedpolyurethanes, polyureas, and polycarbonate-based polyurethanes fillers,and other ingredients, if included, can be blended in either before,during, or after the acid moieties are neutralized, thermoplasticpolyurethanes. Examples of these materials are disclosed in U.S. PatentApplication Publication Nos. 2001/0018375 and 2001/0019971, which areincorporated herein by reference in their entirety.

The ionomer compositions may also include at least one graftedmetallocene catalyzed polymer. Blends of this embodiment may includeabout 1 pph to about 100 pph of at least one grafted metallocenecatalyzed polymer and about 99 pph to 0 pph of at least one ionomer.Where the layer is foamed, the grafted metallocene catalyzed polymerblends may be foamed during molding by any conventional foaming orblowing agent. In addition, polyamides may also be blended withionomers.

The intermediate layer may also include at least one primarily or fullynon-ionomeric thermoplastic material. Suitable non-ionomeric materialsinclude polyamides and polyamide blends, grafted and non-graftedmetallocene catalyzed polyolefins or polyamides, polyamide/ionomerblends, polyamide/nonionomer blends, polyphenylene ether/ionomer blends,and mixtures thereof. Examples of grafted and non-grafted metallocenecatalyzed polyolefins or polyamides, polyamide/ionomer blends,polyamide/nonionomer blends are disclosed in co-pending U.S. patentapplication Ser. No. 10/138,304, filed May 6, 2002, entitled “Golf BallIncorporating Grafted Metallocene Catalyzed Polymer Blends,” the entiredisclosure of which is incorporated by reference herein.

Polyamide homopolymers, such as polyamide 6,18 and polyamide 6,36 may beused alone, or in combination with other polyamide homopolymers. Inanother embodiment, polyamide copolymers, such as polyamide 6,10/6,36,are used alone, or in combination with other polyamide homopolymers orcopolymers. Other examples of suitable polyamide homopolymers andcopolymers include polyamide 4, polyamide 6, polyamide 7, polyamide 11,polyamide 12 (manufactured as Rilsan AMNO by Atofina Chemicals, Inc. ofKing of Prussia, Pa.), polyamide 13, polyamide 4,6, polyamide 6,6,polyamide 6,9, polyamide 6,10, polyamide 6,12, polyamide 6,36, polyamide12,12, polyamide 13,13, polyamide 6/6,6, polyamide 6,6/6,10, polyamide6/6,T wherein T represents terephthalic acid, polyamide 6/6,6/6,10,polyamide 6,10/6,36, polyamide 66,6,18, polyamide 66,6,36, polyamide6/6,18, polyamide 6/6,36, polyamide 6/6,10/6,18, polyamide 6/6,10/6,36,polyamide 6,10/6,18, polyamide 6,12/6,18, polyamide 6,12/6,36, polyamide6/66/6,18, polyamide 6/66/6,36, polyamide 66/6,10/6,18, polyamide66/6,10/6,36, polyamide 6/6,12/6,18, polyamide 6/6,12/6,36, and mixturesthereof.

Nonionomers suitable for blending with the polyamide include, but arenot limited to, block copoly(ester) copolymers, block copoly(amide)copolymers, block copoly(urethane) copolymers, styrene-based blockcopolymers, thermoplastic and elastomer blends wherein the elastomer isnot vulcanized (TEB), and thermoplastic and elastomer or rubber blendswherein the elastomer is dynamically vulcanized (TED). Other nonionomerssuitable for blending with polyamide to form an intermediate layercomposition include, but are not limited to, polycarbonate,polyphenylene oxide, imidized, amino group containing polymers, highimpact polystyrene (HIPS), polyether ketone, polysulfone, poly(phenylenesulfide), reinforced engineering plastics,acrylic-styrene-acrylonitrile, poly(tetrafluoroethylene), poly(butylacrylate), poly(4-cyanobutyl acrylate), poly(2-ethylbutyl acrylate),poly(heptyl acrylate), poly(2-methylbutyl acrylate), poly(3-methylbutylacrylate), poly(N-octadecylacrylamide), poly(octadecyl methacrylate),poly(4-dodecylstyrene), poly(4-tetradecylstyrene), poly(ethylene oxide),poly(oxymethylene), poly(silazane), poly(furan tetracarboxylic aciddiimide), poly(acrylonitrile), poly(methylstyrene), as well as theclasses of polymers to which they belong and their copolymers, includingfunctional comonomers, and blends thereof.

The intermediate layer may include a resilient polymer component, whichis preferably used as the majority polymer in the intermediate layer toimpart resilience in the cured state, and a reinforcing polymercomponent as a blend.

Resilient polymers suitable for use in the intermediate layer includepolybutadiene, polyisoprene, styrene-butadiene, styrene-propylene-dienerubber, ethylene-propylene-diene (EPDM), mixtures thereof, and the like,preferably having a high molecular weight of at least about 50,000 toabout 1,000,000.

The reinforcing polymer component preferably has a glass transitiontemperature (T_(G)) sufficiently low to permit mixing without initiatingcrosslinking, preferably between about 35° C. to 120° C. In addition,the reinforcing polymer component preferably has a sufficiently lowviscosity at the mixing temperature when mixed with the resilientpolymer component to permit proper mixing of the two polymer components.The weight of the reinforcing polymer relative to the total compositionfor forming the intermediate layer generally ranges from about 5 to 25weight percent, preferably about 10 to 20 weight percent.

Examples of polymers suitable for use in the reinforcing polymercomponent include: trans-polyisoprene, block copolymer ether/ester,acrylic polyol, polyethylene, polyethylene copolymer, 1,2-polybutadiene(syndiotactic), ethylene-vinyl acetate copolymer,trans-polycyclooctenenamer, trans-isomer polybutadiene, and mixturesthereof. Particularly suitable reinforcing polymers include: HYTREL3078, a block copolymer ether/ester commercially available from DuPontof Wilmington, Del.; a trans-isomer polybutadiene, such as FUREN 88obtained from Asahi Chemicals of Yako, Kawasakiku, Kawasakishi, Japan;KURRARAY TP251, a trans-polyisoprene commercially available fromKURRARAY CO.; LEVAPREN 700HV, an ethylene-vinyl acetate copolymercommercially available from Bayer-Rubber Division, Akron, Ohio; andVESTENAMER 8012, a trans-polycyclooctenenamer commercially availablefrom Huls America Inc. of Tallmadge, Ohio. Some suitable reinforcingpolymer components are listed in Table 1 below with their crystallinemelt temperature (T_(C)) and/or T_(G).

Another polymer particularly suitable for use in the reinforcing polymercomponent is a rigidifying polybutadiene component, which typicallyincludes at least about 80 percent trans-isomer content with theremainder being cis-isomer 1,4-polybutadiene and vinyl-isomer1,2-polybutadiene. Thus, it may be referred to herein as a “hightrans-isomer polybutadiene” or a “rigidifying polybutadiene” todistinguish it from the cis-isomer polybutadienes or polybutadieneshaving a low trans-isomer content, i.e., typically below 80 percent,used to form the golf ball cores of the invention. The vinyl-content ofthe rigidifying polybutadiene component is preferably present in no morethan about 15 percent, preferably less than about 10 percent, morepreferably less than about 5 percent, and most preferably less thanabout 3 percent of the polybutadiene isomers.

The rigidifying polybutadiene component, when used in a golf ball of theinvention, preferably has a polydispersity of no greater than about 4,preferably no greater than about 3, and more preferably no greater thanabout 2.5. The polydispersity, or PDI, is a ratio of the molecularweight average (M_(w)) over the molecular number average (M_(n)) of apolymer.

In addition, the rigidifying polybutadiene component, when used in agolf ball of the invention, typically has a high absolute molecularweight average, defined as being at least about 100,000, preferably fromabout 200,000 to about 1,000,000. In one embodiment, the absolutemolecular weight average is from about 230,000 to about 750,000. Inanother embodiment, the molecular weight is about 275,000 to about700,000. In any embodiment where the vinyl-content is present in greaterthan about 10 percent, the absolute molecular weight average ispreferably greater than about 200,000.

When trans-polyisoprene or high trans-isomer polybutadiene is includedin the reinforcing polymer component, it may be present in an amount ofabout 10 to about 40 weight percent, preferably about 15 to about 30weight percent, more preferably about 15 to no more than about 25 weightpercent of the polymer blend, i.e., the resilient and reinforcingpolymer components.

The same crosslinking agents mentioned above with regard to the core maybe used in this embodiment to achieve the desired elastic modulus forthe resilient polymer-reinforcing polymer blend. In one embodiment, thecrosslinking agent is added in an amount from about 1 to about 50 pph ofthe polymer blend, preferably about 20 to about 45 pph, and morepreferably about 30 to about 40 pph, of the polymer blend.

The resilient polymer component, reinforcing polymer component,free-radical initiator, and any other materials used in forming anintermediate layer of a golf ball core in accordance with invention maybe combined by any type of mixing known to one of ordinary skill in theart.

The intermediate layer may also be a tensioned elastomeric materialwound around a solid, semi-solid, hollow, fluid-filled, or powder-filledcenter. A wound layer may be described as a core layer or anintermediate layer for the purposes of the invention. As an example, thegolf ball may include a core layer, a tensioned elastomeric layer woundthereon, and a cover layer. The tensioned elastomeric material may beformed of any suitable material known to one of ordinary skill in theart.

In one embodiment, the tensioned elastomeric layer is a high tensilefilament having a tensile modulus of about 10,000 kpsi or greater, asdisclosed in co-pending U.S. Patent Publication No. 2002/0160859, theentire disclosure of which is incorporated by reference herein. Inanother embodiment, the tensioned elastomeric layer is coated with abinding material that will adhere to the core and itself when activated,causing the strands of the tensioned elastomeric layer to swell andincrease the cross-sectional area of the layer by at least about 5percent. An example of such a golf ball construction is provided inco-pending U.S. Patent Publication No. 2002/0160862, the entiredisclosure of which is incorporated by reference herein.

The intermediate layer may also be formed of a binding material and aninterstitial material distributed in the binding material, wherein theeffective material properties of the intermediate layer are uniquelydifferent for applied forces normal to the surface of the ball fromapplied forces tangential to the surface of the ball. Examples of thistype of intermediate layer are disclosed in U.S. Patent Publication No.2003/0125134, the entire disclosure of which is incorporated byreference herein. In one embodiment of the present invention, theinterstitial material may extend from the intermediate layer into thecore. In an alternative embodiment, the interstitial material can alsobe embedded in the cover, or be in contact with the inner surface of thecover, or be embedded only in the cover.

At least one intermediate layer may also be a moisture barrier layer,such as the ones described in U.S. Pat. No. 5,820,488, which isincorporated by reference herein. Any suitable film-forming materialhaving a lower water vapor transmission rate than the other layersbetween the core and the outer surface of the ball, i.e., cover, primer,and clear coat. Examples include, but are not limited to polyvinylidenechloride, vermiculite, and a reaction product with fluorine gas. In oneembodiment, the moisture barrier layer has a water vapor transmissionrate that is sufficiently low to reduce the loss of CoR of the golf ballby at least 5 percent if the ball is stored at 100° F. and 70 percentrelative humidity for six weeks as compared to the loss in COR of a golfball that does not include the moisture barrier, has the same type ofcore and cover, and is stored under substantially identical conditions.

Additional materials may be included in the intermediate layercompositions outlined above. For example, catalysts, coloring agents,optical brighteners, crosslinking agents, whitening agents such as TiO₂and ZnO, UV absorbers, hindered amine light stabilizers, defoamingagents, processing aids, surfactants, and other conventional additivesmay be added to the intermediates. In addition, antioxidants,stabilizers, softening agents, plasticizers, including internal andexternal plasticizers, impact modifiers, foaming agents,density-adjusting fillers, reinforcing materials, and compatibilizersmay also be added to any of the intermediate layer compositions. One ofordinary skill in the art should be aware of the requisite amount foreach type of additive to realize the benefits of that particularadditive.

The intermediate layer, may be formed from using any suitable methodknown to one of ordinary skill in the art, particularly for intermediatelayers that do not include silane-crosslinked polyolefins of the presentinvention. For example, an intermediate layer may be formed by blowmolding and covered with a dimpled cover layer formed by injectionmolding, compression molding, casting, vacuum forming, powder coating,and the like.

For example, castable reactive liquid materials may be applied over theinner ball using a variety of application techniques such as spraying,compression molding, dipping, spin coating, or flow coating methods thatare well known in the art. In one embodiment, the castable reactivematerial is formed over the core using a combination of casting andcompression molding. Conventionally, compression molding and injectionmolding are applied to thermoplastic cover materials, whereas RIM,liquid injection molding, and casting are utilized on thermoset covertechniques.

Cover Layer(s)

The cover provides the interface between the ball and a club. Propertiesthat are desirable for the cover are good moldability, high abrasionresistance, high tear strength, high resilience, and good mold release,among others.

As used herein, the term “cover” means the outermost portion of a golfball. A cover typically includes at least one layer and may containindentations such as dimples and/or ridges. Paints and/or laminates aretypically disposed about the cover to protect the golf ball during usethereof.

Prior to forming the cover layer, the inner ball, i.e., the core and anyintermediate layers disposed thereon, may be surface treated to increasethe adhesion between the outer surface of the inner ball and the cover.Examples of such surface treatment may include mechanically orchemically abrading the outer surface of the subassembly. Additionally,the inner ball may be subjected to corona discharge or plasma treatmentprior to forming the cover around it. Other layers of the ball, e.g.,the core, also may be surface treated. Examples of these and othersurface treatment techniques can be found in U.S. Pat. No. 6,315,915,the entirety of which is incorporated by reference herein.

The cover layer may be comprised of silane-crosslinked polyolefins ofthe present invention and formed using the methods described herein.When a cover layer is not comprised of the silane-crosslinkedpolyolefins of the present invention, it is composed conventionalmaterials known to one of ordinary skill in the art may be used,including thermoplastic and thermosetting materials as discussed below.The one or more silane-crosslinked polyolefins also may be blended withconventional cover layer materials.

For example, the cover can include any suitable cover or cover layermaterials, known to one of ordinary skill in the art, includingthermoplastic and thermosetting materials, but preferably the cover orcover layer can include any suitable materials, such as ionic copolymersof ethylene and an unsaturated monocarboxylic acid which are availableunder the trademark SURLYN of E.I. DuPont de Nemours & Co., ofWilmington, Del., or IOTEK or ESCOR of Exxon. These are copolymers orterpolymers of ethylene and methacrylic acid or acrylic acid partiallyneutralized with salts of zinc, sodium, lithium, magnesium, potassium,calcium, manganese, nickel or the like, in which the salts are thereaction product of an olefin having from 2 to 8 carbon atoms and anunsaturated monocarboxylic acid having 3 to 8 carbon atoms. Thecarboxylic acid groups of the copolymer may be totally or partiallyneutralized and might include methacrylic, crotonic, maleic, fumaric oritaconic acid.

This golf ball can likewise include one or more homopolymeric orcopolymeric cover or cover layer materials, such as:

-   -   (1) Vinyl resins, such as those formed by the polymerization of        vinyl chloride, or by the copolymerization of vinyl chloride        with vinyl acetate, acrylic esters or vinylidene chloride;    -   (2) Polyolefins, such as polyethylene, polypropylene,        polybutylene and copolymers such as ethylene methylacrylate,        ethylene ethylacrylate, ethylene vinyl acetate, ethylene        methacrylic or ethylene acrylic acid or propylene acrylic acid        and copolymers and homopolymers produced using a single-site        catalyst;    -   (3) Polyurethanes, such as those prepared from polyols and        diisocyanates or polyisocyanates and those disclosed in U.S.        Pat. No. 5,334,673;    -   (4) Polyureas, such as those disclosed in U.S. Pat. No.        5,484,870;    -   (5) Polyamides, such as poly(hexamethylene adipamide) and others        prepared from diamines and dibasic acids, as well as those from        amino acids such as poly(caprolactam), and blends of polyamides        with SURLYN, polyethylene, ethylene copolymers,        ethyl-propylene-non-conjugated diene terpolymer, and the like;    -   (6) Acrylic resins and blends of these resins with poly vinyl        chloride, elastomers, and the like;    -   (7) Thermoplastics, such as urethanes; olefinic thermoplastic        rubbers, such as blends of polyolefins with        ethylene-propylene-non-conjugated diene terpolymer; block        copolymers of styrene and butadiene, isoprene or        ethylene-butylene rubber; or copoly(ether-amide), such as PEBAX,        sold by Atofina Chemicals, Inc. of King of Prussia, Pa.;    -   (8) Polyphenylene oxide resins or blends of polyphenylene oxide        with high impact polystyrene as sold under the trademark NORYL        by General Electric Company of Pittsfield, Mass.;    -   (9) Thermoplastic polyesters, such as polyethylene        terephthalate, polybutylene terephthalate, polyethylene        terephthalate/glycol modified and elastomers sold under the        trademarks HYTREL by E.I. DuPont de Nemours & Co. of Wilmington,        Del., and LOMOD by General Electric Company of Pittsfield,        Mass.;    -   (10) Blends and alloys, including polycarbonate with        acrylonitrile butadiene styrene, polybutylene terephthalate,        polyethylene terephthalate, styrene maleic anhydride,        polyethylene, elastomers, and the like, and polyvinyl chloride        with acrylonitrile butadiene styrene or ethylene vinyl acetate        or other elastomers; and    -   (11) Blends of thermoplastic rubbers with polyethylene,        propylene, polyacetal, nylon, polyesters, cellulose esters, and        the like.

Preferably, the cover includes polymers, such as ethylene, propylene,butene-1 or hexane-1 based homopolymers or copolymers includingfunctional monomers, such as acrylic and methacrylic acid and fully orpartially neutralized ionomer resins and their blends, methyl acrylate,methyl methacrylate homopolymers and copolymers, imidized, amino groupcontaining polymers, polycarbonate, reinforced polyamides, polyphenyleneoxide, high impact polystyrene, polyether ketone, polysulfone,poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(ethelyne vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers, and blends thereof. Suitable cover compositions also includea polyether or polyester thermoplastic urethane, a thermosetpolyurethane, a low modulus ionomer, such as acid-containing ethylenecopolymer ionomers, including E/X/Y terpolymers where E is ethylene, Xis an acrylate or methacrylate-based softening comonomer present inabout 0 to 50 weight percent and Y is acrylic or methacrylic acidpresent in about 5 to 35 weight percent. More preferably, in a low spinrate embodiment designed for maximum distance, the acrylic ormethacrylic acid is present in about 15 to 35 weight percent, making theionomer a high modulus ionomer. In a high spin embodiment, the coverincludes an ionomer where an acid is present in about 10 to 15 weightpercent and includes a softening comonomer.

The cover typically has a thickness to provide sufficient strength, goodperformance characteristics and durability. The cover of the golf ballstypically has a thickness of at least about 0.03 inches, preferably 0.03to 0.125 inches, and more preferably from about 0.05 to 0.1 inches. Thegolf balls also typically have at least about 60 percent dimplecoverage, preferably at least about 70 percent dimple coverage, of thesurface area of the cover.

Generally, the covers are formed around the solid or wound cores byeither compression molding preformed half-shells of the cover stockmaterial or by injection molding the cover stock about the core.Half-shells are made by injection molding a cover stock into aconventional half-shell mold in a conventional manner. The preferredmethod is compression molding of preformed half-shells

The cover may include a plurality of layers, e.g., an inner cover layerdisposed about a golf ball center and an outer cover layer formedthereon. For example, the present invention encompasses a golf ballhaving a core, a thin inner cover layer, and a thin outer cover layerdisposed thereon. For example, the core may be formed of are-crosslinked product of the present invention, the inner cover layerformed of an ionomer blend, and the outer cover layer formed of apolyurea composition. In another embodiment, the outer cover layer has adifferent hardness than the inner cover layer.

While hardness gradients are typically used in a golf ball to achievecertain characteristics, the present invention also contemplates thecompositions of the invention being used in a golf ball with multiplecover layers having essentially the same hardness, wherein at least oneof the layers has been modified in some way to alter a property thataffects the performance of the ball. Such ball constructions aredisclosed in co-pending U.S. Patent Publication No. 2003/0232666, theentire disclosure of which is incorporated by reference herein.

In one such embodiment, both covers layers can be formed of the samematerial and have essentially the same hardness, but the layers aredesigned to have different coefficient of friction values. In anotherembodiment, the compositions of the invention are used in a golf ballwith multiple cover layers having essentially the same hardness, butdifferent rheological properties under high deformation. Another aspectof this embodiment relates to a golf ball with multiple cover layershaving essentially the same hardness, but different thicknesses tosimulate a soft outer cover over hard inner cover ball.

In another aspect of this concept, the cover layers of a golf ball haveessentially the same hardness, but different properties at high or lowtemperatures as compared to ambient temperatures. In particular, thisaspect of the invention is directed to a golf ball having multiple coverlayers wherein the outer cover layer composition has a lower flexuralmodulus at reduced temperatures than the inner cover layer, while thelayers retain the same hardness at ambient and reduced temperatures,which results in a simulated soft outer cover layer over a hard innercover layer feel. For example, certain polyureas may have a much morestable flexural modulus at different temperatures than ionomer resinsand thus, could be used to make an effectively “softer” layer at lowertemperatures than at ambient or elevated temperatures.

Yet another aspect of this concept relates to a golf ball with multiplecover layers having essentially the same hardness, but differentproperties under wet conditions as compared to dry conditions.Wettability of a golf ball layer may be affected by surface roughness,chemical heterogeneity, molecular orientation, swelling, and interfacialtensions, among others. Thus, non-destructive surface treatments of agolf ball layer may aid in increasing the hydrophilicity of a layer,while highly polishing or smoothing the surface of a golf ball layer maydecrease wettability. U.S. Pat. Nos. 5,403,453 and 5,456,972 disclosemethods of surface treating polymer materials to affect the wettability,the entire disclosures of which are incorporated by reference herein. Inaddition, plasma etching, corona treating, and flame treating may beuseful surface treatments to alter the wettability to desiredconditions. Wetting agents may also be added to the golf ball layercomposition to modify the surface tension of the layer.

Thus, the differences in wettability of the cover layers according tothe invention may be measured by a difference in contact angle. Thecontact angles for a layer may be from about 10 (low wettability) toabout 180° (very high wettability). In one embodiment, the cover layershave contact angles that vary by about 1° or greater. In anotherembodiment, the contact angles of the cover layers vary by about 3° orgreater. In yet another embodiment, the contact angles of the coverlayers vary by about 5° or greater.

Other non-limiting examples of suitable types of ball constructions thatmay be used with the present invention include those described in U.S.Pat. Nos. 6,056,842, 5,688,191, 5,713,801, 5,803,831, 5,885,172,5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, as well as inPublication Nos. U.S. 2001/0009310 A1, U.S. 2002/0025862, and U.S.2002/0028885. The entire disclosures of these patents and publishedpatent

The cover layer material may be applied over an inner ball using avariety of application techniques such as spraying, compression molding,dipping, spin coating, or flow coating methods that are well known inthe art. In one embodiment, the conventional cover or cover layermaterial is used to form a cover over the core using a combination ofcasting and compression molding. Conventionally, compression molding andinjection molding are applied to thermoplastic cover materials, whereasRIM, liquid injection molding, and casting are employed on thermosetcover materials.

U.S. Pat. No. 5,733,428, the entire disclosure of which is incorporatedby reference herein, discloses a useful method for forming apolyurethane cover on a golf ball core.

For example, once the conventional cover or cover layer material ismixed, an exothermic reaction commences and continues until the materialis solidified around the core. It is important that the viscosity bemeasured over time, so that the subsequent steps of filling each moldhalf, introducing the core into one half and closing the mold can beproperly timed for accomplishing centering of the core cover halvesfusion and achieving overall uniformity. A suitable viscosity range ofthe curing mix for introducing cores into the mold halves is determinedto be approximately between about 2,000 cP and about 30,000 cP, with thepreferred range of about 8,000 cP to about 15,000 cP.

To start the cover formation, mixing of the prepolymer and curative isaccomplished in a motorized mixer inside a mixing head by feedingthrough lines metered amounts of curative and prepolymer. Top preheatedmold halves are filled and placed in fixture units using centering pinsmoving into apertures in each mold. At a later time, the cavity of abottom mold half, or the cavities of a series of bottom mold halves, isfilled with similar mixture amounts as used for the top mold halves.After the reacting materials have resided in top mold halves for about40 to about 100 seconds, preferably for about 70 to about 80 seconds, acore is lowered at a controlled speed into the gelling reacting mixture.

A ball cup holds the ball core through reduced pressure (or partialvacuum). Upon location of the core in the halves of the mold aftergelling for about 4 to about 12 seconds, the vacuum is released allowingthe core to be released. In one embodiment, the vacuum is releasedallowing the core to be released after about 5 seconds to about 10seconds. The mold halves, with core and solidified cover half thereon,are removed from the centering fixture unit, inverted and mated withsecond mold halves which, at an appropriate time earlier, have had aselected quantity of reacting prepolymer and curing agent introducedtherein to commence gelling.

Similarly, U.S. Pat. No. 5,006,297 and U.S. Pat. No. 5,334,673 both alsodisclose suitable molding techniques that may be utilized to apply thecastable reactive liquids employed in the present invention. However,the method of the invention is not limited to the use of thesetechniques; other methods known to those skilled in the art may also beemployed. For instance, other methods for holding the ball core may beutilized instead of using a partial vacuum.

Dimples

The use of various dimple patterns and profiles provides a relativelyeffective way to modify the aerodynamic characteristics of a golf ball.As such, the manner in which the dimples are arranged on the surface ofthe ball can be by any available method. For instance, the ball may havean icosahedron-based pattern, such as described in U.S. Pat. No.4,560,168, or an octahedral-based dimple patterns as described in U.S.Pat. No. 4,960,281.

In one embodiment of the present invention, the golf ball has anicosahedron dimple pattern that includes 20 triangles made from about362 dimples and, except perhaps for the mold parting line, does not havea great circle that does not intersect any dimples. Each of the largetriangles, preferably, has an odd number of dimples (7) along each sideand the small triangles have an even number of dimples (4) along eachside. To properly pack the dimples, the large triangle has nine moredimples than the small triangle. In another embodiment, the ball hasfive different sizes of dimples in total. The sides of the largetriangle have four different sizes of dimples and the small triangleshave two different sizes of dimples.

In another embodiment of the present invention, the golf ball has anicosahedron dimple pattern with a large triangle including threedifferent dimples and the small triangles having only one diameter ofdimple. In a preferred embodiment, there are 392 dimples and one greatcircle that does not intersect any dimples. In another embodiment, morethan five alternative dimple diameters are used.

In one embodiment of the present invention, the golf ball has anoctahedron dimple pattern including eight triangles made from about 440dimples and three great circles that do not intersect any dimples. Inthe octahedron pattern, the pattern includes a third set of dimplesformed in a smallest triangle inside of and adjacent to the smalltriangle. To properly pack the dimples, the large triangle has nine moredimples than the small triangle and the small triangle has nine moredimples than the smallest triangle. In this embodiment, the ball has sixdifferent dimple diameters distributed over the surface of the ball. Thelarge triangle has five different dimple diameters, the small trianglehas three different dimple diameters and the smallest triangle has twodifferent dimple diameters.

Alternatively, the dimple pattern can be arranged according tophyllotactic patterns, such as described in U.S. Pat. No. 6,338,684,which is incorporated herein in its entirety.

Dimple patterns may also be based on Archimedean patterns including atruncated octahedron, a great rhombcuboctahedron, a truncateddodecahedron, and a great rhombicosidodecahedron, wherein the patternhas a non-linear parting line, as disclosed in U.S. patent applicationSer. No. 10/078,417, which is incorporated by reference herein.

The golf balls of the present invention may also be covered withnon-circular shaped dimples, i.e., amorphous shaped dimples, asdisclosed in U.S. Pat. No. 6,409,615, which is incorporated in itsentirety by reference herein.

Dimple patterns that provide a high percentage of surface coverage arepreferred, and are well known in the art. For example, U.S. Pat. Nos.5,562,552, 5,575,477, 5,957,787, 5,249,804, and 4,925,193 disclosegeometric patterns for positioning dimples on a golf ball. In oneembodiment, the golf balls of the invention have a dimple coverage ofthe surface area of the cover of at least about 60 percent, preferablyat least about 65 percent, and more preferably at least 70 percent orgreater. Dimple patterns having even higher dimple coverage values mayalso be used with the present invention. Thus, the golf balls of thepresent invention may have a dimple coverage of at least about 75percent or greater, about 80 percent or greater, or even about 85percent or greater.

In addition, a tubular lattice pattern, such as the one disclosed inU.S. Pat. No. 6,290,615, which is incorporated by reference in itsentirety herein, may also be used with golf balls of the presentinvention. The golf balls of the present invention may also have aplurality of pyramidal projections disposed on the intermediate layer ofthe ball, as disclosed in U.S. Pat. No. 6,383,092, which is incorporatedin its entirety by reference herein. The plurality of pyramidalprojections on the golf ball may cover between about 20 percent to about80 of the surface of the intermediate layer.

In an alternative embodiment, the golf ball may have a non-planarparting line allowing for some of the plurality of pyramidal projectionsto be disposed about the equator. Such a golf ball may be fabricatedusing a mold as disclosed in co-pending U.S. patent application Ser. No.09/442,845, filed Nov. 18, 1999, entitled “Mold For A Golf Ball,” andwhich is incorporated in its entirety by reference herein. Thisembodiment allows for greater uniformity of the pyramidal projections.

Several additional non-limiting examples of dimple patterns with varyingsizes of dimples are also provided in U.S. Pat. No. 6,358,161 and U.S.Pat. No. 6,213,898, the entire disclosures of which are incorporated byreference herein.

The total number of dimples on the ball, or dimple count, may varydepending on such factors as the dimple size and the selected pattern.In general, the total number of dimples on the ball preferably isbetween about 100 to about 1000 dimples, although one skilled in the artwould recognize that differing dimple counts within this range cansignificantly alter the flight performance of the ball. In oneembodiment, the dimple count is about 380 dimples or greater, but morepreferably is about 400 dimples or greater, and even more preferably isabout 420 dimples or greater. In one embodiment, the dimple count on theball is about 422 dimples. In some cases, it may be desirable to havefewer dimples on the ball. Thus, one embodiment of the present inventionhas a dimple count of about 380 dimples or less, and more preferably isabout 350 dimples or less.

Dimple profiles revolving a catenary curve about its symmetrical axismay increase aerodynamic efficiency, provide a convenient way to alterthe dimples to adjust ball performance without changing the dimplepattern, and result in uniformly increased flight distance for golfersof all swing speeds. Thus, catenary curve dimple profiles, as disclosedin U.S. Patent Publication No. 2003/0114255, which is incorporated inits entirety by reference herein, is contemplated for use with the golfballs of the present invention.

Golf Ball Post-Processing

The golf balls of the present invention may be painted, coated, orsurface treated for further benefits. For example, golf balls coversfrequently contain a fluorescent material and/or a dye or pigment toachieve the desired color characteristics. A golf ball of the inventionmay also be treated with a base resin paint composition, however, asdisclosed in U.S. Patent Publication No. 2002/0082358, which includes a7-triazinylamino-3-phenylcoumarin derivative as the fluorescentwhitening agent to provide improved weather resistance and brightness.

In addition, trademarks or other indicia may be stamped, i.e.,pad-printed, on the outer surface of the ball cover, and the stampedouter surface is then treated with at least one clear coat to give theball a glossy finish and protect the indicia stamped on the cover.

The golf balls of the invention may also be subjected to dyesublimation, wherein at least one golf ball component is subjected to atleast one sublimating ink that migrates at a depth into the outersurface and forms an indicia. The at least one sublimating inkpreferably includes at least one of an azo dye, a nitroarylamine dye, oran anthraquinone dye. U.S. Patent Publication No. 2003/0106442, theentire disclosure of which is incorporated by reference herein.

Laser marking of a selected surface portion of a golf ball causing thelaser light-irradiated portion to change color is also contemplated foruse with the present invention. U.S. Pat. Nos. 5,248,878 and 6,075,223generally disclose such methods, the entire disclosures of which areincorporated by reference herein. In addition, the golf balls may besubjected to ablation, i.e., directing a beam of laser radiation onto aportion of the cover, irradiating the cover portion, wherein theirradiated cover portion is ablated to form a detectable mark, whereinno significant discoloration of the cover portion results therefrom.Ablation is discussed in U.S. Pat. No. 6,462,303, the entirety of whichis incorporated by reference herein.

Protective and decorative coating materials, as well as methods ofapplying such materials to the surface of a golf ball cover, are wellknown in the golf ball art. Generally, such coating materials includeurethanes, urethane hybrids, epoxies, polyesters and acrylics. Ifdesired, more than one coating layer can be used. The coating layer(s)may be applied by any suitable method known to one of ordinary skill inthe art. In one embodiment, the coating layer(s) is applied to the golfball cover by an in-mold coating process, such as described in U.S. Pat.No. 5,849,168, which is incorporated in its entirety by referenceherein.

Golf Ball Properties

The properties such as hardness, modulus, core diameter, intermediatelayer thickness and cover layer thickness of the golf balls of thepresent invention have been found to effect play characteristics such asspin, initial velocity and feel of the present golf balls. For example,the flexural and/or tensile modulus of the intermediate layer arebelieved to have an effect on the “feel” of the golf balls of thepresent invention.

Component Dimensions

Dimensions of golf ball components, i.e., thickness and diameter, mayvary depending on the desired properties. For the purposes of theinvention, any layer thickness may be employed. Non-limiting examples ofthe various embodiments outlined above are provided here with respect tolayer dimensions.

The present invention relates to golf balls of any size. While “TheRules of Golf” by the USGA dictate specifications that limit the size ofa competition golf ball to more than 1.680 inches in diameter, golfballs of any size can be used for leisure golf play. The preferreddiameter of the golf balls is from about 1.680 inches to about 1.800inches. The more preferred diameter is from about 1.680 inches to about1.760 inches. A diameter of from about 1.680 inches to about 1.740inches is most preferred, however diameters anywhere in the range offrom 1.700 to about 1.950 inches can be used. Preferably, the overalldiameter of the core and all intermediate layers is about 80 percent toabout 98 percent of the overall diameter of the finished ball.

The core may have a diameter ranging from about 0.090 inches to about1.650 inches. In one embodiment, the diameter of the core of the presentinvention is about 1.200 inches to about 1.630 inches. In anotherembodiment, the diameter of the core is about 1.300 inches to about1.600 inches, preferably from about 1.390 inches to about 1.600 inches,and more preferably from about 1.500 inches to about 1.600 inches. Inyet another embodiment, the core has a diameter of about 1.550 inches toabout 1.650 inches.

The core of the golf ball may also be extremely large in relation to therest of the ball. For example, in one embodiment, the core makes upabout 90 percent to about 98 percent of the ball, preferably about 94percent to about 96 percent of the ball. In this embodiment, thediameter of the core is preferably about 1.540 inches or greater,preferably about 1.550 inches or greater. In one embodiment, the corediameter is about 1.590 inches or greater. In another embodiment, thediameter of the core is about 1.640 inches or less.

When the core includes an inner core layer and an outer core layer, theinner core layer is preferably about 0.9 inches or greater and the outercore layer preferably has a thickness of about 0.1 inches or greater. Inone embodiment, the inner core layer has a diameter from about 0.09inches to about 1.2 inches and the outer core layer has a thickness fromabout 0.1 inches to about 0.8 inches. In yet another embodiment, theinner core layer diameter is from about 0.095 inches to about 1.1 inchesand the outer core layer has a thickness of about 0.20 inches to about0.03 inches.

The cover typically has a thickness to provide sufficient strength, goodperformance characteristics, and durability. In one embodiment, thecover thickness is from about 0.02 inches to about 0.35 inches. Thecover preferably has a thickness of about 0.02 inches to about 0.12inches, preferably about 0.1 inches or less. When the compositions ofthe invention are used to form the outer cover of a golf ball, the covermay have a thickness of about 0.1 inches or less, preferably about 0.07inches or less. In one embodiment, the outer cover has a thickness fromabout 0.02 inches to about 0.07 inches. In another embodiment, the coverthickness is about 0.05 inches or less, preferably from about 0.02inches to about 0.05 inches. In yet another embodiment, the outer coverlayer is between about 0.02 inches to about 0.045 inches. In stillanother embodiment, the outer cover layer is about 0.025 to about 0.04inches thick. In one embodiment, the outer cover layer is about 0.03inches thick.

In some embodiments, a hemispherical shell is typically formed first.The hemispherical shell generally has an outer radius of from about 0.45inches to about 0.900 inches and a thickness from about 0.001 inches toabout 0.500 inches. The outer radius and thickness varies depending onwhether the hemispherical shell is formed for a cover, intermediatelayer or a core layer, as disclosed herein

The range of thicknesses for an intermediate layer of a golf ball islarge because of the vast possibilities when using an intermediatelayer, i.e., as an outer core layer, an inner cover layer, a woundlayer, a moisture/vapor barrier layer. When used in a golf ball of theinvention, the intermediate layer, or inner cover layer, may have athickness about 0.3 inches or less. In one embodiment, the thickness ofthe intermediate layer is from about 0.002 inches to about 0.1 inches,preferably about 0.01 inches or greater. In one embodiment, thethickness of the intermediate layer is about 0.09 inches or less,preferably about 0.06 inches or less. In another embodiment, theintermediate layer thickness is about 0.05 inches or less, morepreferably about 0.01 inches to about 0.045 inches. In one embodiment,the intermediate layer, thickness is about 0.02 inches to about 0.04inches. In another embodiment, the intermediate layer thickness is fromabout 0.025 inches to about 0.035 inches. In yet another embodiment, thethickness of the intermediate layer is about 0.035 inches thick. Instill another embodiment, the inner cover layer is from about 0.03inches to about 0.035 inches thick. Varying combinations of these rangesof thickness for the intermediate and outer cover layers may be used incombination with other embodiments described herein.

The ratio of the thickness of the intermediate layer to the outer coverlayer is preferably about 10 or less, preferably from about 3 or less.In another embodiment, the ratio of the thickness of the intermediatelayer to the outer cover layer is about 1 or less.

The core and intermediate layer(s) together form an inner ballpreferably having a diameter of about 1.48 inches or greater for a1.68-inch ball. In one embodiment, the inner ball of a 1.68-inch ballhas a diameter of about 1.52 inches or greater. In another embodiment,the inner ball of a 1.68-inch ball has a diameter of about 1.66 inchesor less. In yet another embodiment, a 1.72-inch (or more) ball has aninner ball diameter of about 1.50 inches or greater. In still anotherembodiment, the diameter of the inner ball for a 1.72-inch ball is about1.70 inches or less.

Hardness

The molding process and composition of golf ball portions typicallyresults in a gradient of material properties. Methods employed in theprior art generally exploit hardness to quantify these gradients. Mostgolf balls consist of layers having different hardnesses, e.g., hardnessgradients, to achieve desired performance characteristics. The presentinvention contemplates golf balls having hardness gradients betweenlayers, as well as those golf balls with layers having the samehardness.

It should be understood, especially to one of ordinary skill in the art,that there is a fundamental difference between “material hardness” and“hardness, as measured directly on a golf ball.” Material hardness isdefined by the procedure set forth in ASTM-D2240-00 and generallyinvolves measuring the hardness of a flat “slab” or “button” formed ofthe material of which the hardness is to be measured. Generally,ASTM-D2240-00 requires calibration of durometers, which have scalereadings from 0 to 100. However, readings below 10 or above 90 are notconsidered reliable, as noted in ASTM-D2240-00, and accordingly, all thehardness values herein are within this range. Hardness, when measureddirectly on a golf ball (or other spherical surface) is a completelydifferent measurement and, therefore, results in a different hardnessvalue. This difference results from a number of factors including, butnot limited to, ball construction (i.e., core type, number of coreand/or cover layers, etc.), ball (or sphere) diameter, and the materialcomposition of adjacent layers. Hardness is a qualitative measure ofstatic modulus and does not represent the modulus of the material at thedeformation rates associated with golf ball use, i.e., impact by a club.As is well known to one skilled in the art of polymer science, thetime-temperature superposition principle may be used to emulatealternative deformation rates. For golf ball portions includingpolybutadiene, a 1-Hz oscillation at temperatures between 0° C. and −50°C. are believed to be qualitatively equivalent to golf ball impactrates. Therefore, measurements of loss tangent and dynamic stiffness at0° C. to −50° C. may be used to accurately anticipate golf ballperformance, preferably at temperatures between about −20° C. and −50°C. It should also be understood that the two measurement techniques arenot linearly related and, therefore, one hardness value cannot easily becorrelated to the other.

The cores of the present invention may have varying hardnesses, i.e.,surface hardness, depending on the particular golf ball construction, aswell as whether it is formed from the silane-crosslinked polyolefins ofthe present invention, conventional core materials or a combinationthereof. In one embodiment, the core hardness is at least about 15 ShoreA, preferably about 30 Shore A, as measured on a formed sphere. Inanother embodiment, the core has a hardness of about 50 Shore A to about90 Shore D. In yet another embodiment, the hardness of the core is about80 Shore D or less. In another embodiment, the core has a hardness ofabout 20 Shore C to about 90 Shore C, and preferably from about 30 ShoreC to about 90 Shore C. In yet another embodiment, the core has ahardness of about 20 Shore C to about 80 Shore D, preferably from about20 Shore D to about 70 Shore D. Preferably, the core has a hardnessabout 30 to about 65 Shore D, and more preferably, the core has ahardness about 35 to about 60 Shore D. As mentioned above, the upper andlower limits of the ranges disclosed herein are interchangeable to formnew ranges. For example, the hardness of the core may be from about 20Shore D to about 80 Shore D, or 50 Shore A to about 65 Shore D.

The core may have a hardness gradient, i.e., a first hardness at a firstpoint, i.e., at an interior location, and a second hardness at a secondpoint, i.e., at an exterior surface, as measured on a molded sphere. Inone embodiment, the second hardness is at least about 6 percent greaterthan the first hardness, preferably about 10 percent greater than thefirst hardness. In other embodiments, the second hardness is at leastabout 20 percent greater or at least about 30 percent greater, than thefirst hardness.

For example, the interior of the core may have a first hardness of about45 Shore C to about 60 Shore C and the exterior surface of the core mayhave a second hardness of about 65 Shore C to about 75 Shore C. In onegolf ball formulated according to the invention, the first hardness wasabout 51 Shore C and a second hardness was about 71 Shore C, providing ahardness difference of greater than 20 percent.

In one embodiment, however, the core has a substantially uniformhardness throughout. Thus, in this aspect, the first and second hardnesspreferably differ by about 5 percent or less, more preferably about 3percent or less, and even more preferably by about 2 percent or less. Inanother embodiment, the hardness is uniform throughout the component.

The intermediate layer(s) of the present invention may also vary inhardness depending on the specific construction of the ball, as well aswhether it is formed from silane-crosslinked polyolefins of the presentinvention, conventional intermediate layer materials, or a combinationthereof. In one embodiment, the hardness of the intermediate layer isabout 30 Shore D or greater. In another embodiment, the hardness of theintermediate layer is about 90 Shore D or less, preferably about 80Shore D or less, and more preferably about 70 Shore D or less. In yetanother embodiment, the hardness of the intermediate layer is about 40Shore D or greater, preferably about 50 Shore D or greater. In oneembodiment, the intermediate layer hardness is from about 30 Shore D toabout 90 Shore D, and preferably from about 45 Shore D to about 80 ShoreD. In another embodiment, the intermediate layer hardness is from about50 Shore D to about 70 Shore D. The intermediate layer may also be about65 Shore D or greater.

When the intermediate layer is intended to be harder than the corelayer, the ratio of the intermediate layer hardness to the core hardnesspreferably about 2 or less. In one embodiment, the ratio is about 1.8 orless. In yet another embodiment, the ratio is about 1.3 or less.

As with the core and intermediate layers, the cover hardness may varydepending on the construction and desired characteristics of the golfball, as well as whether it is formed from silane-crosslinkedpolyolefins of the present invention. The ratio of cover hardness toinner ball hardness is a primary variable used to control theaerodynamics of a ball and, in particular, the spin of a ball. Ingeneral, the harder the inner ball, the greater the driver spin and thesofter the cover, the greater the driver spin.

For example, when the intermediate layer is intended to be the hardestpoint in the ball, e.g., about 50 Shore D to about 75 Shore D, the covermaterial may have a hardness of about 20 Shore D or greater, preferablyabout 25 Shore D or greater, and more preferably about 30 Shore D orgreater, as measured on the slab. In one embodiment, the cover has ahardness of about 20 Shore A to about 70 Shore D. In another embodiment,the cover itself has a hardness from about 30 Shore D to about 60 ShoreD. In one embodiment, the cover has a hardness of about 40 Shore D toabout 65 Shore D. In another embodiment, the cover has a hardness lessthan about 45 Shore D, preferably less than about 40 Shore D, and morepreferably about 25 Shore D to about 40 Shore D. In yet anotherembodiment, the cover hardness is from about 35 to 80 Shore D,preferably from about 45 to 70 Shore D.

In this embodiment when the outer cover layer is softer than theintermediate layer or inner cover layer, the ratio of the Shore Dhardness of the outer cover material to the intermediate layer materialis about 0.8 or less, preferably about 0.75 or less, and more preferablyabout 0.7 or less. In another embodiment, the ratio is about 0.5 orless, preferably about 0.45 or less.

In yet another embodiment, the ratio is about 0.1 or less when the coverand intermediate layer materials have hardnesses that are substantiallythe same. When the hardness differential between the cover layer and theintermediate layer is not intended to be as significant, the cover mayhave a hardness of about 55 Shore D to about 65 Shore D. In thisembodiment, the ratio of the Shore D hardness of the outer cover to theintermediate layer is about 1.0 or less, preferably about 0.9 or less.

In another embodiment, the cover layer is harder than the intermediatelayer. In this design, the ratio of Shore D hardness of the cover layerto the intermediate layer is about 1.33 or less, preferably from about1.14 or less.

When a two-piece ball is constructed, the core may be softer than theouter cover. For example, the core hardness may range from about 30Shore D to about 50 Shore D, and the cover hardness may be from about 50Shore D to about 80 Shore D. In this type of construction, the ratiobetween the cover hardness and the core hardness is preferably about1.75 or less. In another embodiment, the ratio is about 1.55 or less.Depending on the materials, for example, if a composition of theinvention is acid-functionalized wherein the acid groups are at leastpartially neutralized, the hardness ratio of the cover to core ispreferably about 1.25 or less.

Compression

Depending on the desired properties, balls prepared according to theinvention can exhibit substantially the same or higher resilience, orcoefficient of restitution (CoR), with a decrease in compression ormodulus, compared to balls of conventional construction. As used herein,the term “coefficient of restitution” (CoR) is calculated by dividingthe rebound velocity of the golf ball by the incoming velocity when agolf ball is shot out of an air cannon. The CoR testing is conductedover a range of incoming velocities and determined at an inboundvelocity of 125 ft/s. Additionally, balls prepared according to theinvention can also exhibit substantially higher resilience, orcoefficient of restitution (CoR), without an increase in compression,compared to balls of conventional construction. Another measure of thisresilience is the “loss tangent,” or tan δ, which is obtained whenmeasuring the dynamic stiffness of an object. Loss tangent andterminology relating to such dynamic properties is typically describedaccording to ASTM D4092-90. Thus, a lower loss tangent indicates ahigher resiliency, thereby indicating a higher rebound capacity. Lowloss tangent indicates that most of the energy imparted to a golf ballfrom the club is converted to dynamic energy, i.e., launch velocity andresulting longer distance. The rigidity or compressive stiffness of agolf ball may be measured, for example, by the dynamic stiffness. Ahigher dynamic stiffness indicates a higher compressive stiffness. Toproduce golf balls having a desirable compressive stiffness, the dynamicstiffness of the crosslinked material should be less than about 50,000N/m at −50° C. Preferably, the dynamic stiffness should be between about10,000 and 40,000 N/m at −50° C., more preferably, the dynamic stiffnessshould be between about 20,000 and 30,000 N/m at −50° C.

The dynamic stiffness is similar in some ways to dynamic modulus.Dynamic stiffness is dependent on probe geometry as described herein,whereas dynamic modulus is a unique material property, independent ofgeometry. The dynamic stiffness measurement has the unique attribute ofenabling quantitative measurement of dynamic modulus and exactmeasurement of loss tangent at discrete points within a sample article.In the case of this invention, the article is a golf ball core. The golfball material preferably has a loss tangent below about 0.1 at −50° C.,and more preferably below about 0.07 at −50° C.

The resultant golf balls typically have a coefficient of restitution ofabout 0.7 or more. In another embodiment, the ball has a COR of about0.75 or more, and more preferably is about 0.78 or more. In anotherembodiment, the golf ball has a CoR from about 0.7 to about 0.815. Inyet another embodiment, the ball has a CoR of about 0.79 or more, andmore preferably is about 0.8 or more. Additionally, in each of theseembodiments it is also preferred that the COR of the ball is less thanabout 0.819. Alternatively, the maximum COR of the ball is one that doesnot cause the golf ball to exceed initial velocity requirementsestablished by regulating entities such as the USPGA.

The golf balls also typically have an Atti compression (which has beenreferred to as PGA compression in the past) of at least about 40,preferably from about 50 to 120, and more preferably from about 60 to100. As used herein, the term “Atti compression” is defined as thedeflection of an object or material relative to the deflection of acalibrated spring, as measured with an Atti Compression Gauge, that iscommercially available from Atti Engineering Corp. of Union City, N.J.Atti compression is typically used to measure the compression of a golfball and/or a golf ball core. Compression values are dependent on thediameter of the article being measured. The golf ball polybutadienematerial typically has a flexural modulus of from about 500 psi to300,000 psi, preferably from about 2000 to 200,000 psi. The golf ballpolybutadiene material typically has a hardness of at least about 15Shore A, preferably between about 30 Shore A and 80 Shore D, morepreferably between about 50 Shore A and 60 Shore D. The specific gravityis typically greater than about 0.7, preferably greater than about 1,for the golf ball polybutadiene material. The dynamic shear storagemodulus, or storage modulus, of the golf ball polybutadiene material atabout 23° C. is typically at least about 10,000 dyn/cm², preferably fromabout 10⁴-10¹⁰ dyn/cm², more preferably from about 10⁶ to 10¹⁰ dyn/cm².

Compression values are dependent on the diameter of the component beingmeasured. The Atti compression of the core, or portion of the core, ofgolf balls prepared according to the invention is preferably less thanabout 80, more preferably less than about 75. In another embodiment, thecore compression is from about 40 to about 80, preferably from about 50to about 70. In yet another embodiment, the core compression ispreferably below about 50, and more preferably below about 25.

In an alternative, low compression embodiment, the core has acompression less than about 20, more preferably less than about 10, andmost preferably, O. As known to one of ordinary skill in the art,however, the cores generated according to the present invention may bebelow the measurement of the Atti Compression Gauge. In an embodimentwhere the core is hard, the compression may be about 90 or greater. Inone embodiment, the compression of the hard core ranges from about 90 toabout 100.

Initial Velocity and COR

The present invention encompasses golf balls that conform and meet withUSGA initial velocity requirements. There is currently no USGA limit onthe COR of a golf ball, but the initial velocity of the golf ball cannotexceed the current USGA limit of 250±5 feet/second (ft/s). Thus, in oneembodiment, the initial velocity is about 245 ft/s or greater and about255 ft/s or less. In another embodiment, the initial velocity is about250 ft/s or greater. In another embodiment, the initial velocity isabout 253 ft/s to about 254 ft/s. While the current rules on initialvelocity require that golf ball manufacturers stay within the limit, oneof ordinary skill in the art would appreciate that the golf ball of theinvention would readily convert into a golf ball with initial velocityoutside of this range. For golf balls intended for use as practiceballs, the initial velocity may be below 250 ft/s, and even below 240ft/s.

As a result, of the initial velocity limitation set forth by the USGA,the goal is to maximize COR without violating the 255 ft/s limit. In aone-piece solid golf ball, the COR will depend on a variety ofcharacteristics of the ball, including its composition and hardness. Fora given composition, COR will generally increase as hardness isincreased. In a two-piece solid golf ball, e.g., a core and a cover, oneof the purposes of the cover is to produce a gain in COR over that ofthe core. When the contribution of the core to high COR is substantial,a lesser contribution is required from the cover. Similarly, when thecover contributes substantially to high COR of the ball, a lessercontribution is needed from the core.

The present invention encompasses golf balls that have a COR from about0.7 to about 0.85. In one embodiment, the COR is about 0.75 or greater,preferably about 0.78 or greater. In another embodiment, the ball has aCOR of about 0.8 or greater.

In addition, the inner ball preferably has a COR of about 0.780 or more.In one embodiment, the COR is about 0.790 or greater.

Flexural Modulus

Accordingly, it is preferable that the golf balls of the presentinvention have an intermediate layer with a flexural modulus of about500 psi to about 500,000 psi. More preferably, the flexural modulus ofthe intermediate layer is about 1,000 psi to about 250,000 psi. Mostpreferably, the flexural modulus of the intermediate layer is about2,000 psi to about 200,000 psi.

The flexural modulus of the cover on the golf balls, as measured by ASTMmethod D-6272-98, is typically greater than about 500 psi, and ispreferably from about 500 psi to about 150,000 psi. The flexural moduliof the cover layer is preferably about 2,000 psi or greater, and morepreferably about 5,000 psi or greater. In one embodiment, the flexuralmoduli of the cover is from about 10,000 psi to about 150,000 psi, morepreferably from about 15,000 psi to about 120,000 psi, and mostpreferably from about 18,000 psi to about 110,000 psi. In anotherembodiment, the flexural moduli of the cover layer is about 100,000 psior less, preferably about 80,000 or less, and more preferably about70,000 psi or less. In one embodiment, when the cover layer has ahardness of about 50 Shore D to about 60 Shore D, the cover layerpreferably has a flexural modulus of about 55,000 psi to about 65,000psi.

In one embodiment, the ratio of the flexural modulus of the intermediatelayer to the cover layer is about 0.003 to about 50. In anotherembodiment, the ratio of the flexural modulus of the intermediate layerto the cover layer is about 0.006 to about 4.5. In yet anotherembodiment, the ratio of the flexural modulus of the intermediate layerto the cover layer is about 0.11 to about 4.5.

In one embodiment, the compositions of the invention are used in a golfball with multiple cover layers having essentially the same hardness,but differences in flexural moduli. In this aspect of the invention, thedifference between the flexural moduli of the two cover layers ispreferably about 5,000 psi or less. In another embodiment, thedifference in flexural moduli is about 500 psi or greater. In yetanother embodiment, the difference in the flexural moduli between thetwo cover layers, wherein at least one is reinforced is about 500 psi toabout 10,000 psi, preferably from about 500 psi to about 5,000 psi. Inone embodiment, the difference in flexural moduli between the two coverlayers formed of unreinforced or unmodified materials is about 1,000 psito about 2,500 psi.

Specific Gravity and Shear/Cut Resistance

The specific gravity of a cover or intermediate layer including thecompositions of the invention is preferably at least about 0.7. Inanother embodiment, the specific gravity of a cover or intermediatelayer including the compositions of the invention is at least about 0.6.In yet another embodiment, the specific gravity of the cover orintermediate layer is at last about 1.0, preferably at least about 0.9and more preferably at least about 0.8.

The specific gravity of a core including the compositions of theinvention is greater than 1.5, more preferably greater than 1.8 and morepreferably greater than 2.0. In another embodiment, the specific gravityof the fore including the compositions of the invention is greater than2.5, and can be as high as 5.0 and 10.0.

The cut resistance of a golf ball cover may be determined using a sheartest having a scale from 1 to 9 assessing damage and appearance. Thescale for this shear test is known to one of ordinary skill in the art.In one embodiment, the damage rank is preferably about 3 or less, morepreferably about 2 or less. In another embodiment, the damage rank isabout 1 or less. The appearance rank of a golf ball of the invention ispreferably about 3 or less. In one embodiment, the appearance rank isabout 2 or less, preferably about 1 or less.

Ball Spin

A spin rate of a golf ball refers to the speed it spins on an axis whilein flight, measured in revolutions per minute (“rpm”). Spin generateslift, and accordingly, spin rate directly influences how high the ballflies and how quickly it stops after landing. The golf balls disclosedherein can be tested to determine spin rate by initially establishingtest conditions using suitable control golf balls and golf clubs. Forexample, a spin rate of a golf ball struck by a standard golf driver wasobtained by using test conditions for a Titleist Pinnacle Gold golf ballthat gives a ball speed of about 159 to about 161 miles/hour, a launchangle of about 9.0 degrees to about 10.0 degrees, and a spin rate ofabout 2900 rpm to about 3100 rpm. Thus in one embodiment, the spin rateof a golf ball hit with a golf club driver under the same testconditions is between about 1200 rpm to about 4000 rpm. In a preferredembodiment, the spin rate of a golf ball hit with a golf club driver isbetween about 2000 rpm to about 3500 rpm, more preferably between about2500 and 3000 rpm.

For an 8-iron ball spin test, a spin rate of a golf ball struck by astandard 8-iron club was obtained by using test conditions for aTitleist Pro V1 golf ball that gives a ball speed of about 114 to about116 miles/hour, a launch angle of about 18.5 to about 19.5 degrees and aspin rate of about 8100 rpm to about 8300 rpm. Thus in one embodiment,the spin rate of an average, cleanly struck 8-iron shot is between 6500rpm and 10,000 rpm. In preferred embodiment, the spin rate of anaverage, cleanly struck 8-iron shot under the same test conditions isbetween 7500 rpm and 9500 rpm, more preferably between about 8000 rpmand 9000 rpm.

Other than in the operating examples, or unless otherwise expresslyspecified, all of the numerical ranges, amounts, values and percentagessuch as those for amounts of materials, times and temperatures ofreaction, ratios of amounts, values for molecular weight (whether numberaverage molecular weight (“Mn”) or weight average molecular weight(“Mw”), and others in the following portion of the specification may beread as if prefaced by the word “about” even though the term “about” maynot expressly appear with the value, amount or range. Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present invention. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

While it is apparent that the invention disclosed herein is wellcalculated to fulfill the objects stated above, it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art. For example, while golf balls and golf ballcomponents are used as examples for articles incorporating thecompositions of the invention, other golf equipment is contemplated,such as portions of golf shoes and portions of golf clubs. Therefore, itis intended that the appended claims cover all such modifications andembodiments that fall within the true spirit and scope of the presentinvention.

We claim:
 1. A method of forming a golf ball comprising the steps of:forming a silane-grafted polyolefin by copolymerizing at least onesilane with at least one polyolefin in the presence of a graftinginitiator; crosslinking the silane-grafted polyolefin in the presence ofmoisture to form a crosslinked silane-grafted polyolefin; forming a golfball component consisting essentially of the crosslinked silane-graftedpolyolefin; and forming a golf ball cover disposed on the golf ballcomponent.
 2. The method of claim 1, wherein the at least one silane hasa formula of:

wherein X is a hydrolysable group, and n is 0-24; wherein R′ is a vinylgroup is represented by the formula:

wherein R₁, R₂, and R₃ are each independently selected from the groupconsisting of a substituted or unsubstituted linear or branched C₁-C₈alkyl group, a substituted or unsubstituted C₆-C₁₂ aromatic group and ahalo group; and wherein the substituted linear or branched C₁-C₈ alkylgroup and the substituted C₆-C₁₂ aromatic group is substituted with atleast one C₁-C₆ alkyl group, halo group, amine, CN, C₁-C₆ alkoxy group,or trihalomethane group.
 3. The method of claim 2, wherein X is selectedfrom the group consisting of alkoxy, acyloxy, halogen, amino, hydrogen,ketoximate group, amido group, aminooxy, mercapto, and alkenyloxy. 4.The method of claim 1, wherein the at least one grafting initiator isselected from the group consisting of di-tert-amyl peroxide,di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy)diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butyl-peroxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and a mixture thereof, wherein thegrafting initiator is present from about 0.1 weight percent to about 15weight percent of the silane; and wherein the at least one polyolefin isselected from the group consisting of low-density polyethylene,high-density polyethylene, linear low-density polyethylene, ultra highmolecular weight polyethylene, metallocene polyethylene, ametallocene-catalyzed polyolefin, and mixtures thereof.
 5. The method ofclaim 1, wherein the golf ball component is a core layer or anintermediate layer.
 6. The method of claim 1, wherein the step ofcrosslinking further comprises exposing the silane-grafted polyolefin toa crosslinking catalyst, wherein the crosslinking catalyst comprises atin catalyst or a platinum catalyst, and wherein the crosslinkingcatalyst is present in an amount from about 0.1 weight percent to about15 weight percent of the reaction mixture.
 7. The method of claim 1,wherein the moisture is from about 30% to 100% relative humidity and ata temperature between about 20° C. to about 100° C. for a timesufficient to substantially complete crosslinking of the reactionmixture.
 8. The method of claim 7, wherein the relative humidity isbetween about 50% to about 80% and the time is between about 30 minutesto about 24 hours.
 9. The method of claim 1, further comprising the stepof injection molding or compression molding the silane-graftedpolyolefin prior to the step of crosslinking.
 10. A method of forming agolf ball comprising the steps of: forming a silane-grafted polyolefinby copolymerizing at least one silane with at least one polyolefin inthe presence of a grafting initiator; molding the silane-graftedpolyolefin into an intermediate component; exposing the intermediatecomponent to a crosslinking catalyst and moisture to form an innercomponent consisting essentially of a silane-crosslinked polyolefin; andforming a cover disposed about the inner component.
 11. The method ofclaim 1, wherein the step of forming a silane-grafted polyolefin furthercomprises contacting a metallocene-catalyzed polyolefin with thegrafting initiator.
 12. The method of claim 1, further comprising thesteps of molding the silane-grafted polyolefin into an intermediatecomponent; exposing the intermediate component to moisture to form aninner component consisting essentially of a silane-crosslinkedpolyolefin; and forming a golf ball cover disposed about the innercomponent.
 13. The method of claim 10, wherein the grafting initiator isselected from the group consisting of di-tert-amyl peroxide,di(2-tert-butyl-peroxyisopropyl)benzene peroxide orα,α-bis(tert-butylperoxy)diisopropylbenzene,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane or1,1-di(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, dicumyl peroxide,di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(tert-butyl-peroxy)valerate, lauryl peroxide, benzoylperoxide, tert-butyl hydroperoxide, and a mixture thereof, wherein thegrafting initiator is present from about 0.1 weight percent to about 15weight percent of the silane; and wherein the at least one polyolefin isselected from the group consisting of low-density polyethylene,high-density polyethylene, linear low-density polyethylene, ultra highmolecular weight polyethylene, metallocene polyethylene, ametallocene-catalyzed polyolefin, and mixtures thereof.
 14. The methodof claim 10, wherein the step of molding comprises compression moldingthe silane-grafted polyolefin into a cup.
 15. The method of claim 10,wherein the step of molding comprises injection molding thesilane-grafted polyolefin.
 16. The method of claim 10, wherein thesilane-grafted polyolefin comprises a monomer of a metallocene-catalyzedpolyolefin.
 17. The method of claim 10, wherein the crosslinkingcatalyst comprises a tin catalyst or a platinum catalyst, and whereinthe crosslinking catalyst is present in an amount from about 0.1 weightpercent to about 15 weight percent of the reaction mixture.
 18. Themethod of claim 10, wherein the at least one silane has a formula of:

wherein X is a hydrolysable group, and n is 0-24; wherein R′ is a vinylgroup is represented by the formula:

wherein R₁, R₂, and R₃ are each independently selected from the groupconsisting of a substituted or unsubstituted linear or branched C₁-C₈alkyl group, a substituted or unsubstituted C₆-C₁₂ aromatic group and ahalo group; and wherein the substituted linear or branched C₁-C₈ alkylgroup and the substituted C₆-C₁₂ aromatic group is substituted with atleast one C₁-C₆ alkyl group, halo group, amine, CN, C₁-C₆ alkoxy group,or trihalomethane group.
 19. The method of claim 18, wherein X isselected from the group consisting of alkoxy, acyloxy, halogen, amino,hydrogen, ketoximate group, amido group, aminooxy, mercapto, andalkenyloxy.
 20. The method of claim 10, wherein the moisture is fromabout 30% to 100% relative humidity and at a temperature between about20° C. to about 100° C. for a time sufficient to substantially completecrosslinking of the silane-grafted polyolefin.